It has been widely used and selected by systemd as defalut scheduling algorithm
since v217.
https://github.com/systemd/systemd/blob/master/NEWS#L5861



Signed-off-by: He Zhe <zhe.he@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Signed-off-by: Armin Kuster <akuster808@gmail.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

1/1 [
Author: Bruce Ashfield
Email: bruce.ashfield@gmail.com
Subject: arch/x86/boot: use prefix map to avoid embedded paths
Date: Thu, 8 Aug 2019 23:39:26 -0400

It was observed that the kernel embeds the path in the x86 boot
artifacts.

From https://bugzilla.yoctoproject.org/show_bug.cgi?id=13458

:

[
   If you turn on the buildpaths QA test, or try a reproducible build, you
   discover that the kernel image contains build paths.

   $ strings bzImage-5.0.19-yocto-standard |grep tmp/
   out of pgt_buf in
   /data/poky-tmp/reproducible/tmp/work-shared/qemux86-64/kernel-source/arch/x86/boot/compressed/kaslr_64.c!?

   But what's this in the top-level Makefile:

   $ git grep prefix-map
   Makefile:KBUILD_CFLAGS  += $(call
   cc-option,-fmacro-prefix-map=$(srctree)/=)

   So the __FILE__ shouldn't be using the full path.  However
   arch/x86/boot/compressed/Makefile has this:

   KBUILD_CFLAGS := -m$(BITS) -O2

   So that clears KBUILD_FLAGS, removing the -fmacro-prefix-map option.
]

Other architectures do not clear the flags, but instead prune before
adding boot or specific options. There's no obvious reason why x86 isn't
doing the same thing (pruning vs clearing) and no build or boot issues
have been observed.

So we make x86 can do the same thing, and we no longer have embedded paths.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

This enables this configuration to be included for intel-common BSP used
by meta-intel.

Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Enabling this would make the kernel trust CPU's random number generator
for the purposes of initializing CRNG.

Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Disable fallback to gain full whitelist enforcement.

Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Because CONFIG_DEV_DAX* are not supported in preempt-rt kernel, use
two scc files for Non-RT kerel and RT kernel separately.

Signed-off-by: Yongxin Liu <yongxin.liu@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Enable CONFIG_DRM_MGAG200=m to support Matrox Electronics MGA G200
and include it in intel-x86 bsp.

Signed-off-by: Liwei Song <liwei.song@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Signed-off-by: He Zhe <zhe.he@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Purpose: Support booting a beaglebone image with runqemu.

If the kernel supports Qemu's virt machine, runqemu works almost for free.
The device tree for machine virt is included in Qemu, which simplifies
everything quite a bit.
This change adds ARCH_VIRT=y and some drivers to the beaglebone kernel
configuration which allows to:

  export MACHINE="beaglebone-yocto"
  bitbake core-image-minimale
  runqemu

This also works out of an eSDK. Whithout this feature usually two different
SDKs need to be compiled and maintained. One SDK is used for development
in Qemu, another one is used to develop for the real target hardware.

[Yocto #13384]

Signed-off-by: Adrian Freihofer <adrian.freihofer@siemens.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

This patch is to create the minimum set for cpu idle/freq scaling, which is ok
to both arm and arm64 with DT enablement. And we leave more specific features
to the end users.

Signed-off-by: Zumeng.Chen <zumeng.chen@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

This patch is to add scc/cfg meta to build and boot zcu102 board with the bsp
of xilinx-zynqmp.

Signed-off-by: Zumeng.Chen <zumeng.chen@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

The ptests from util-linux require the scsi debug module to be installed
for a subset of tests. This patch would allow to build the kernel module
for the linux-yocto kernel.

Signed-off-by: Mariano López <just.another.mariano@gmail.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Commit dc41fe5d6fb5 [ARM: fix function graph tracer and unwinder
dependencies] enforces that we can't have the unwinder and the
graph trace enabled at the same time.

There is broader use for the unwind functionality, so we explicitly
disable the graph tracer for arch/arm.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

1/9 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: genirq: Handle missing work_struct in irq_set_affinity_notifier()
Date: Tue, 28 May 2019 10:42:15 +0200

The backported stable commit
   59c39840f5abf ("genirq: Prevent use-after-free and work list corruption")

added cancel_work_sync() on a work_struct element which is not available
in RT.

Replace cancel_work_sync() with kthread_cancel_work_sync() on RT.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

2/9 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: v5.0.19-rt10
Date: Wed, 29 May 2019 10:18:43 +0200

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

3/9 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: locking/lockdep: Don't complain about incorrect name for no validate class
Date: Fri, 17 May 2019 23:22:34 +0200

[ Upstream commit 978315462d3ea3cf6cfacd34c563ec1eb02a3aa5 ]

It is possible to ignore the validation for a certain lock by using:

	lockdep_set_novalidate_class()

on it. Each invocation will assign a new name to the class it created
for created __lockdep_no_validate__. That means that once
lockdep_set_novalidate_class() has been used on two locks then
class->name won't match lock->name for the first lock triggering the
warning.

So ignore changed non-matching ->name pointer for the special
__lockdep_no_validate__ class.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20190517212234.32611-1-bigeasy@linutronix.de


Signed-off-by: Ingo Molnar <mingo@kernel.org>
]

4/9 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: arm: imx6: cpuidle: Use raw_spinlock_t
Date: Tue, 14 May 2019 17:07:44 +0200

The idle call back is invoked with disabled interrupts and requires
raw_spinlock_t locks to work.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

5/9 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: clocksource: TCLIB: Add proper depend
Date: Wed, 29 May 2019 15:50:36 +0200

Add a depends statement on ATMEL_TCLIB to ensure that it is not built on !ATMEL
if COMPILE_TEST is enabled. The build will fail because the driver depends on
`atmel_tc_divisors'.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

6/9 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: Revert "drm/i915/fence: Do not use TIMER_IRQSAFE"
Date: Wed, 29 May 2019 21:09:09 +0200

The TIMER_IRQSAFE flag is required because the i915 cancels timer from
interrupt.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

7/9 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: softirq: rework
Date: Wed, 29 May 2019 18:47:32 +0200

This is an all-one patch which contains the softirq rework.
The basic idea is to have local-lock within local_bh_disable() which is
used for synchronisation similar to mainline. With this synchronisation
we can't have two softirqs processed in parallel on the same CPU. This
allows to remove the extra synchronisation we had.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

8/9 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: workqueue: rework
Date: Wed, 29 May 2019 18:52:27 +0200

This is an all-in change of the workqueue rework.
The worker_pool.lock is made to raw_spinlock_t. With this change we can
schedule workitems from preempt-disable sections and sections with disabled
interrupts. This change allows to remove all kthread_.* workarounds we used to
have.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

9/9 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: v5.0.19-rt11
Date: Wed, 29 May 2019 21:23:39 +0200

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

1/25 [
Author: Hongxu Jia
Email: hongxu.jia@windriver.com
Subject: genirq: Prevent use-after-free and work list corruption on rt
Date: Sat, 18 May 2019 11:31:41 -0400

Since commit [70a44a0 genirq: Prevent use-after-free and work list
corruption] applied, the patch makes it work on rt

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

2/25 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: v5.0.7-rt4
Date: Wed, 10 Apr 2019 16:52:35 +0200

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

3/25 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86: load FPU registers on return to userland (Update to v9)
Date: Wed, 10 Apr 2019 17:23:26 +0200

This is an incremental change to update the patch series from v7 to v9
as posted on Date: Wed,  3 Apr 2019 18:41:29 +0200.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

4/25 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: clocksource: improve Atmel TCB timer driver
Date: Tue, 30 Apr 2019 18:27:59 +0200

This is an icremental update from
  [PATCH 00/12] clocksource: improve Atmel TCB timer driver
to
  [PATCH v3 0/9] clocksource: improve Atmel TCB timer driver

as posted on Fri, 26 Apr 2019 23:47:17 +0200 by Alexandre Belloni.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

5/25 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: drm/i915: Don't disable interrupts independently of the lock
Date: Wed, 10 Apr 2019 11:01:37 +0200

The locks (timeline->lock and rq->lock) need to be taken with disabled
interrupts. This is done in __retire_engine_request() by disabling the
interrupts independently of the locks itself.
While local_irq_disable()+spin_lock() equals spin_lock_irq() on vanilla
it does not on RT. Also, it is not obvious if there is a special reason
to why the interrupts are disabled independently of the lock.

Enable/disable interrupts as part of the locking instruction.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

6/25 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: v5.0.7-rt5
Date: Fri, 12 Apr 2019 21:57:48 +0200

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

7/25 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: v5.0.10-rt6
Date: Tue, 30 Apr 2019 16:19:30 +0200

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

8/25 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Fault-in user stack if copy_fpstate_to_sigframe() fails
Date: Fri, 10 May 2019 11:49:47 +0200

[
  cherry pick commit d9c9ce34ed5c892323cbf5b4f9a4c498e036316a which
  replaces commit 6c0731d83879c994cc2e2f8eab52e22231737e48 and
  294e8631fbd27bc3727e7052cc4dc27ff7ff1320 (in this tree).
]

In the compacted form, XSAVES may save only the XMM+SSE state but skip
FP (x87 state).

This is denoted by header->xfeatures = 6. The fastpath
(copy_fpregs_to_sigframe()) does that but _also_ initialises the FP
state (cwd to 0x37f, mxcsr as we do, remaining fields to 0).

The slowpath (copy_xstate_to_user()) leaves most of the FP
state untouched. Only mxcsr and mxcsr_flags are set due to
xfeatures_mxcsr_quirk(). Now that XFEATURE_MASK_FP is set
unconditionally, see

  04944b793e18 ("x86: xsave: set FP, SSE bits in the xsave header in the user sigcontext"),

on return from the signal, random garbage is loaded as the FP state.

Instead of utilizing copy_xstate_to_user(), fault-in the user memory
and retry the fast path. Ideally, the fast path succeeds on the second
attempt but may be retried again if the memory is swapped out due
to memory pressure. If the user memory can not be faulted-in then
get_user_pages() returns an error so we don't loop forever.

Fault in memory via get_user_pages_unlocked() so
copy_fpregs_to_sigframe() succeeds without a fault.

Fixes: 69277c98f5eef ("x86/fpu: Always store the registers in copy_fpstate_to_sigframe()")
Reported-by: Kurt Kanzenbach <kurt.kanzenbach@linutronix.de>
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>
Cc: Qian Cai <cai@lca.pw>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190502171139.mqtegctsg35cir2e@linutronix.de


Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

9/25 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Remove unnecessary saving of FPU registers in copy_fpstate_to_sigframe()
Date: Tue, 30 Apr 2019 10:31:26 +0200

Since commit:

  eeec00d73be2e ("x86/fpu: Fault-in user stack if copy_fpstate_to_sigframe() fails")

there is no need to have FPU registers saved if
copy_fpregs_to_sigframe() fails, because we retry it after we resolved
the fault condition.

Saving the registers is not wrong but it is not necessary and it forces us
to load the FPU registers on the retry attempt.

Don't save the FPU registers if copy_fpstate_to_sigframe() fails.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jason@zx2c4.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bp@suse.de
Cc: jannh@google.com
Cc: kurt.kanzenbach@linutronix.de
Cc: kvm@vger.kernel.org
Cc: pbonzini@redhat.com
Cc: riel@surriel.com
Cc: rkrcmar@redhat.com
Link: http://lkml.kernel.org/r/20190430083126.rilbb76yc27vrem5@linutronix.de


Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

10/25 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: locking/rwsem: Rename rwsem_rt.h to rwsem-rt.h
Date: Tue, 30 Apr 2019 18:15:19 +0200

Rename rwsem_rt.h to rwsem-rt.h to remain consistent with rwsem-rt.c.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

11/25 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: kmsg_dump: remove mutex usage
Date: Wed, 24 Apr 2019 16:36:04 +0200

The kmsg dumper can be called from any context, but the dumping
helpers were using a mutex to synchronize the iterator against
concurrent dumps.

Rather than trying to synchronize the iterator, use a local copy
of the iterator during the dump. Then no synchronization is
required.

Reported-by: Scott Wood <swood@redhat.com>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

12/25 [
Author: Scott Wood
Email: swood@redhat.com
Subject: x86/ima: Check EFI_RUNTIME_SERVICES before using
Date: Tue, 23 Apr 2019 17:48:07 -0500

Checking efi_enabled(EFI_BOOT) is not sufficient to ensure that
EFI runtime services are available, e.g. if efi=noruntime is used.

Without this, I get an oops on a PREEMPT_RT kernel where efi=noruntime is
the default.

Fixes: 399574c64eaf94e8 ("x86/ima: retry detecting secure boot mode")
Signed-off-by: Scott Wood <swood@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

13/25 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: clocksource: improve Atmel TCB timer driver
Date: Tue, 30 Apr 2019 18:27:59 +0200

This is an icremental update from
  [PATCH 00/12] clocksource: improve Atmel TCB timer driver
to
  [PATCH v3 0/9] clocksource: improve Atmel TCB timer driver

as posted on Fri, 26 Apr 2019 23:47:17 +0200 by Alexandre Belloni.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

14/25 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: v5.0.10-rt7
Date: Tue, 30 Apr 2019 18:31:09 +0200

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

15/25 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: v5.0.14-rt8
Date: Fri, 10 May 2019 11:23:29 +0200

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

16/25 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Fault-in user stack if copy_fpstate_to_sigframe() fails
Date: Fri, 10 May 2019 11:49:47 +0200

[
  cherry pick commit d9c9ce34ed5c892323cbf5b4f9a4c498e036316a which
  replaces commit 6c0731d83879c994cc2e2f8eab52e22231737e48 and
  294e8631fbd27bc3727e7052cc4dc27ff7ff1320 (in this tree).
]

In the compacted form, XSAVES may save only the XMM+SSE state but skip
FP (x87 state).

This is denoted by header->xfeatures = 6. The fastpath
(copy_fpregs_to_sigframe()) does that but _also_ initialises the FP
state (cwd to 0x37f, mxcsr as we do, remaining fields to 0).

The slowpath (copy_xstate_to_user()) leaves most of the FP
state untouched. Only mxcsr and mxcsr_flags are set due to
xfeatures_mxcsr_quirk(). Now that XFEATURE_MASK_FP is set
unconditionally, see

  04944b793e18 ("x86: xsave: set FP, SSE bits in the xsave header in the user sigcontext"),

on return from the signal, random garbage is loaded as the FP state.

Instead of utilizing copy_xstate_to_user(), fault-in the user memory
and retry the fast path. Ideally, the fast path succeeds on the second
attempt but may be retried again if the memory is swapped out due
to memory pressure. If the user memory can not be faulted-in then
get_user_pages() returns an error so we don't loop forever.

Fault in memory via get_user_pages_unlocked() so
copy_fpregs_to_sigframe() succeeds without a fault.

Fixes: 69277c98f5eef ("x86/fpu: Always store the registers in copy_fpstate_to_sigframe()")
Reported-by: Kurt Kanzenbach <kurt.kanzenbach@linutronix.de>
Suggested-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>
Cc: Qian Cai <cai@lca.pw>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190502171139.mqtegctsg35cir2e@linutronix.de


Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

17/25 [
Author: Julien Grall
Email: julien.grall@arm.com
Subject: genirq/msi: Add a new field in msi_desc to store an IOMMU cookie
Date: Wed, 1 May 2019 14:58:18 +0100

[Upstream commit aaebdf8d68479f78d9f72b239684f70fbb0722c6]

When an MSI doorbell is located downstream of an IOMMU, it is required
to swizzle the physical address with an appropriately-mapped IOVA for any
device attached to one of our DMA ops domain.

At the moment, the allocation of the mapping may be done when composing
the message. However, the composing may be done in non-preemtible
context while the allocation requires to be called from preemptible
context.

A follow-up change will split the current logic in two functions
requiring to keep an IOMMU cookie per MSI.

A new field is introduced in msi_desc to store an IOMMU cookie. As the
cookie may not be required in some configuration, the field is protected
under a new config CONFIG_IRQ_MSI_IOMMU.

A pair of helpers has also been introduced to access the field.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

18/25 [
Author: Julien Grall
Email: julien.grall@arm.com
Subject: iommu/dma-iommu: Split iommu_dma_map_msi_msg() in two parts
Date: Wed, 1 May 2019 14:58:19 +0100

[ Upstream commit ece6e6f0218b7777e650bf93728130ae6f4feb7d]

On RT, iommu_dma_map_msi_msg() may be called from non-preemptible
context. This will lead to a splat with CONFIG_DEBUG_ATOMIC_SLEEP as
the function is using spin_lock (they can sleep on RT).

iommu_dma_map_msi_msg() is used to map the MSI page in the IOMMU PT
and update the MSI message with the IOVA.

Only the part to lookup for the MSI page requires to be called in
preemptible context. As the MSI page cannot change over the lifecycle
of the MSI interrupt, the lookup can be cached and re-used later on.

iomma_dma_map_msi_msg() is now split in two functions:
    - iommu_dma_prepare_msi(): This function will prepare the mapping
    in the IOMMU and store the cookie in the structure msi_desc. This
    function should be called in preemptible context.
    - iommu_dma_compose_msi_msg(): This function will update the MSI
    message with the IOVA when the device is behind an IOMMU.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

19/25 [
Author: Julien Grall
Email: julien.grall@arm.com
Subject: irqchip/gicv2m: Don't map the MSI page in gicv2m_compose_msi_msg()
Date: Wed, 1 May 2019 14:58:20 +0100

[Upstream commit 737be74710f30e611ee871f7b4f47975d1c6f71a ]

gicv2m_compose_msi_msg() may be called from non-preemptible context.
However, on RT, iommu_dma_map_msi_msg() requires to be called from a
preemptible context.

A recent change split iommu_dma_map_msi_msg() in two new functions:
one that should be called in preemptible context, the other does
not have any requirement.

The GICv2m driver is reworked to avoid executing preemptible code in
non-preemptible context. This can be achieved by preparing the MSI
mapping when allocating the MSI interrupt.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

20/25 [
Author: Julien Grall
Email: julien.grall@arm.com
Subject: irqchip/gic-v3-its: Don't map the MSI page in its_irq_compose_msi_msg()
Date: Wed, 1 May 2019 14:58:21 +0100

[ Upstream commit 35ae7df21be098848722f96f0f33bf33467436a8 ]

its_irq_compose_msi_msg() may be called from non-preemptible context.
However, on RT, iommu_dma_map_msi_msg requires to be called from a
preemptible context.

A recent change split iommu_dma_map_msi_msg() in two new functions:
one that should be called in preemptible context, the other does
not have any requirement.

The GICv3 ITS driver is reworked to avoid executing preemptible code in
non-preemptible context. This can be achieved by preparing the MSI
mapping when allocating the MSI interrupt.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

21/25 [
Author: Julien Grall
Email: julien.grall@arm.com
Subject: irqchip/ls-scfg-msi: Don't map the MSI page in ls_scfg_msi_compose_msg()
Date: Wed, 1 May 2019 14:58:22 +0100

[ Upstream commit 2cb3b16545495ee31dc9438f88232c2cfe44a41f ]

ls_scfg_msi_compose_msg() may be called from non-preemptible context.
However, on RT, iommu_dma_map_msi_msg() requires to be called from a
preemptible context.

A recent patch split iommu_dma_map_msi_msg() in two new functions:
one that should be called in preemptible context, the other does
not have any requirement.

The FreeScale SCFG MSI driver is reworked to avoid executing preemptible
code in non-preemptible context. This can be achieved by preparing the
MSI maping when allocating the MSI interrupt.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

22/25 [
Author: Julien Grall
Email: julien.grall@arm.com
Subject: irqchip/gic-v3-mbi: Don't map the MSI page in mbi_compose_m{b, s}i_msg()
Date: Wed, 1 May 2019 14:58:23 +0100

[ Upstream commit 73103975425786ebdb6c4d2868ecf26f391fb77e ]

The functions mbi_compose_m{b, s}i_msg may be called from non-preemptible
context. However, on RT, iommu_dma_map_msi_msg() requires to be called
from a preemptible context.

A recent patch split iommu_dma_map_msi_msg in two new functions:
one that should be called in preemptible context, the other does
not have any requirement.

The GICv3 MSI driver is reworked to avoid executing preemptible code in
non-preemptible context. This can be achieved by preparing the MSI
mapping when allocating the MSI interrupt.

Signed-off-by: Julien Grall <julien.grall@arm.com>
[maz: only call iommu_dma_prepare_msi once, fix commit log accordingly]
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

23/25 [
Author: Julien Grall
Email: julien.grall@arm.com
Subject: iommu/dma-iommu: Remove iommu_dma_map_msi_msg()
Date: Wed, 1 May 2019 14:58:24 +0100

[ Upstream commit 16e32c3cde7763ab875b9030b443ecbc8e352d8a ]

A recent change split iommu_dma_map_msi_msg() in two new functions. The
function was still implemented to avoid modifying all the callers at
once.

Now that all the callers have been reworked, iommu_dma_map_msi_msg() can
be removed.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Acked-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

24/25 [
Author: Corey Minyard
Email: cminyard@mvista.com
Subject: sched/completion: Fix a lockup in wait_for_completion()
Date: Thu, 9 May 2019 14:33:20 -0500

Consider following race:

  T0                    T1                       T2
  wait_for_completion()
   do_wait_for_common()
    __prepare_to_swait()
     schedule()
                        complete()
                         x->done++ (0 -> 1)
                         raw_spin_lock_irqsave()
                         swake_up_locked()       wait_for_completion()
                          wake_up_process(T0)
                          list_del_init()
                         raw_spin_unlock_irqrestore()
                                                  raw_spin_lock_irq(&x->wait.lock)
  raw_spin_lock_irq(&x->wait.lock)                x->done != UINT_MAX, 1 -> 0
                                                  raw_spin_unlock_irq(&x->wait.lock)
                                                  return 1
   while (!x->done && timeout),
   continue loop, not enqueued
   on &x->wait

Basically, the problem is that the original wait queues used in
completions did not remove the item from the queue in the wakeup
function, but swake_up_locked() does.

Fix it by adding the thread to the wait queue inside the do loop.
The design of swait detects if it is already in the list and doesn't
do the list add again.

Cc: stable-rt@vger.kernel.org
Fixes: a04ff6b4ec4ee7e ("completion: Use simple wait queues")
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
[bigeasy: shorten commit message ]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

25/25 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: v5.0.14-rt9
Date: Fri, 10 May 2019 13:20:49 +0200

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Enable support for the USB RNDIS host driver.  This is commonly seen
with Android devices being used in USB tether mode.

Signed-off-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Enable CONFIG_VMD=y to support Intel VMD and VROC feature.

Signed-off-by: Liwei Song <liwei.song@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

The only way to boot from Intel VROC RAID disk is use initramfs with
mdadm installed, mdadm is used to initialize RAID volume and create
md device, During initialization it need read RAID status from efivarfs,
so efivarfs must be ready before mdadm initialize RAID volume

built-in efivarfs to kernel can aviod the timing problem and make mdadm
work well.

Signed-off-by: Liwei Song <liwei.song@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

change CONFIG_BLK_DEV_NVME=m to CONFIG_BLK_DEV_NVME=y to build-in
nvme driver to kernel to support boot from nvme disk.

Signed-off-by: Liwei Song <liwei.song@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

This is a first attempt at enabling some missing config items
in a -tiny configuration that are required for boot.

This is not a complete configuration, since there are still issues
with the hvc console, but it does enable us to boot and login.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

As Indicated by Richard Purdie, in order to shutdown the machine we have
to explicitly enable the PIIX4 poweroff driver for the
qemumips/qemumips64 after the kernel commit dd129c6374e9 ("MIPS: Malta:
Use PIIX4 poweroff driver to power down") is merged.

Signed-off-by: Kevin Hao <kexin.hao@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

In the following commits, these two options have been replaced by
CONFIG_AUDITSYSCALL which is in audit.cfg.

c8fc5d49c341 ("audit: remove WATCH and TREE config options")
cb74ed278f80 ("audit: always enable syscall auditing when supported and audit is enabled")

Signed-off-by: He Zhe <zhe.he@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

The following upstream commits have renamed INTEL_RDT to RESCTRL.
6fe07ce35e8a ("x86/resctrl: Rename the config option INTEL_RDT to RESCTRL")
e6d429313ea5 ("x86/resctrl: Avoid confusion over the new X86_RESCTRL config")

Signed-off-by: He Zhe <zhe.he@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

1/298 [
Author: Alexandre Belloni
Email: alexandre.belloni@bootlin.com
Subject: ARM: at91: add TCB registers definitions
Date: Thu, 13 Sep 2018 13:30:18 +0200

Add registers and bits definitions for the timer counter blocks found on
Atmel ARM SoCs.

Tested-by: Alexander Dahl <ada@thorsis.com>
Tested-by: Andras Szemzo <szemzo.andras@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

2/298 [
Author: Alexandre Belloni
Email: alexandre.belloni@bootlin.com
Subject: clocksource/drivers: Add a new driver for the Atmel ARM TC blocks
Date: Thu, 13 Sep 2018 13:30:19 +0200

Add a driver for the Atmel Timer Counter Blocks. This driver provides a
clocksource and two clockevent devices.

One of the clockevent device is linked to the clocksource counter and so it
will run at the same frequency. This will be used when there is only on TCB
channel available for timers.

The other clockevent device runs on a separate TCB channel when available.

This driver uses regmap and syscon to be able to probe early in the boot
and avoid having to switch on the TCB clocksource later. Using regmap also
means that unused TCB channels may be used by other drivers (PWM for
example). read/writel are still used to access channel specific registers
to avoid the performance impact of regmap (mainly locking).

Tested-by: Alexander Dahl <ada@thorsis.com>
Tested-by: Andras Szemzo <szemzo.andras@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

3/298 [
Author: Alexandre Belloni
Email: alexandre.belloni@bootlin.com
Subject: clocksource/drivers: timer-atmel-tcb: add clockevent device on separate channel
Date: Thu, 13 Sep 2018 13:30:20 +0200

Add an other clockevent device that uses a separate TCB channel when
available.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

4/298 [
Author: Alexandre Belloni
Email: alexandre.belloni@bootlin.com
Subject: clocksource/drivers: atmel-pit: make option silent
Date: Thu, 13 Sep 2018 13:30:21 +0200

To conform with the other option, make the ATMEL_PIT option silent so it
can be selected from the platform

Tested-by: Alexander Dahl <ada@thorsis.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

5/298 [
Author: Alexandre Belloni
Email: alexandre.belloni@bootlin.com
Subject: ARM: at91: Implement clocksource selection
Date: Thu, 13 Sep 2018 13:30:22 +0200

Allow selecting and unselecting the PIT clocksource driver so it doesn't
have to be compile when unused.

Tested-by: Alexander Dahl <ada@thorsis.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

6/298 [
Author: Alexandre Belloni
Email: alexandre.belloni@bootlin.com
Subject: ARM: configs: at91: use new TCB timer driver
Date: Thu, 13 Sep 2018 13:30:23 +0200

Unselecting ATMEL_TCLIB switches the TCB timer driver from tcb_clksrc to
timer-atmel-tcb.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

7/298 [
Author: Alexandre Belloni
Email: alexandre.belloni@bootlin.com
Subject: ARM: configs: at91: unselect PIT
Date: Thu, 13 Sep 2018 13:30:24 +0200

The PIT is not required anymore to successfully boot and may actually harm
in case preempt-rt is used because the PIT interrupt is shared.
Disable it so the TCB clocksource is used.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

8/298 [
Author: Julia Cartwright
Email: julia@ni.com
Subject: kthread: convert worker lock to raw spinlock
Date: Fri, 28 Sep 2018 21:03:51 +0000

In order to enable the queuing of kthread work items from hardirq
context even when PREEMPT_RT_FULL is enabled, convert the worker
spin_lock to a raw_spin_lock.

This is only acceptable to do because the work performed under the lock
is well-bounded and minimal.

Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Guenter Roeck <linux@roeck-us.net>
Reported-and-tested-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Reported-by: Tim Sander <tim@krieglstein.org>
Signed-off-by: Julia Cartwright <julia@ni.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

9/298 [
Author: Peter Zijlstra
Email: peterz@infradead.org
Subject: sched/fair: Robustify CFS-bandwidth timer locking
Date: Mon, 7 Jan 2019 13:52:31 +0100

Traditionally hrtimer callbacks were run with IRQs disabled, but with
the introduction of HRTIMER_MODE_SOFT it is possible they run from
SoftIRQ context, which does _NOT_ have IRQs disabled.

Allow for the CFS bandwidth timers (period_timer and slack_timer) to
be ran from SoftIRQ context; this entails removing the assumption that
IRQs are already disabled from the locking.

While mainline doesn't strictly need this, -RT forces all timers not
explicitly marked with MODE_HARD into MODE_SOFT and trips over this.
And marking these timers as MODE_HARD doesn't make sense as they're
not required for RT operation and can potentially be quite expensive.

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reported-by: Tom Putzeys <tom.putzeys@be.atlascopco.com>
Tested-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190107125231.GE14122@hirez.programming.kicks-ass.net


Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

10/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk-rb: add printk ring buffer documentation
Date: Tue, 12 Feb 2019 15:29:39 +0100

The full documentation file for the printk ring buffer.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

11/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk-rb: add prb locking functions
Date: Tue, 12 Feb 2019 15:29:40 +0100

Add processor-reentrant spin locking functions. These allow
restricting the number of possible contexts to 2, which can simplify
implementing code that also supports NMI interruptions.

    prb_lock();

    /*
     * This code is synchronized with all contexts
     * except an NMI on the same processor.
     */

    prb_unlock();

In order to support printk's emergency messages, a
processor-reentrant spin lock will be used to control raw access to
the emergency console. However, it must be the same
processor-reentrant spin lock as the one used by the ring buffer,
otherwise a deadlock can occur:

    CPU1: printk lock -> emergency -> serial lock
    CPU2: serial lock -> printk lock

By making the processor-reentrant implemtation available externally,
printk can use the same atomic_t for the ring buffer as for the
emergency console and thus avoid the above deadlock.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

12/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk-rb: define ring buffer struct and initializer
Date: Tue, 12 Feb 2019 15:29:41 +0100

See Documentation/printk-ringbuffer.txt for details about the
initializer arguments.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

13/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk-rb: add writer interface
Date: Tue, 12 Feb 2019 15:29:42 +0100

Add the writer functions prb_reserve() and prb_commit(). These make
use of processor-reentrant spin locks to limit the number of possible
interruption scenarios for the writers.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

14/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk-rb: add basic non-blocking reading interface
Date: Tue, 12 Feb 2019 15:29:43 +0100

Add reader iterator static declaration/initializer, dynamic
initializer, and functions to iterate and retrieve ring buffer data.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

15/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk-rb: add blocking reader support
Date: Tue, 12 Feb 2019 15:29:44 +0100

Add a blocking read function for readers. An irq_work function is
used to signal the wait queue so that write notification can
be triggered from any context.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

16/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk-rb: add functionality required by printk
Date: Tue, 12 Feb 2019 15:29:45 +0100

The printk subsystem needs to be able to query the size of the ring
buffer, seek to specific entries within the ring buffer, and track
if records could not be stored in the ring buffer.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

17/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: add ring buffer and kthread
Date: Tue, 12 Feb 2019 15:29:46 +0100

The printk ring buffer provides an NMI-safe interface for writing
messages to a ring buffer. Using such a buffer for alleviates printk
callers from the current burdens of disabled preemption while calling
the console drivers (and possibly printing out many messages that
another task put into the log buffer).

Create a ring buffer to be used for storing messages to be
printed to the consoles.

Create a dedicated printk kthread to block on the ring buffer
and call the console drivers for the read messages.

NOTE: The printk_delay is relocated to _after_ the message is
      printed, where it makes more sense.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

18/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: remove exclusive console hack
Date: Tue, 12 Feb 2019 15:29:47 +0100

In order to support printing the printk log history when new
consoles are registered, a global exclusive_console variable is
temporarily set. This only works because printk runs with
preemption disabled.

When console printing is moved to a fully preemptible dedicated
kthread, this hack no longer works.

Remove exclusive_console usage.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

19/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: redirect emit/store to new ringbuffer
Date: Tue, 12 Feb 2019 15:29:48 +0100

vprintk_emit and vprintk_store are the main functions that all printk
variants eventually go through. Change these to store the message in
the new printk ring buffer that the printk kthread is reading.

Remove functions no longer in use because of the changes to
vprintk_emit and vprintk_store.

In order to handle interrupts and NMIs, a second per-cpu ring buffer
(sprint_rb) is added. This ring buffer is used for NMI-safe memory
allocation in order to format the printk messages.

NOTE: LOG_CONT is ignored for now and handled as individual messages.
      LOG_CONT functions are masked behind "#if 0" blocks until their
      functionality can be restored

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

20/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk_safe: remove printk safe code
Date: Tue, 12 Feb 2019 15:29:49 +0100

vprintk variants are now NMI-safe so there is no longer a need for
the "safe" calls.

NOTE: This also removes printk flushing functionality.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

21/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: minimize console locking implementation
Date: Tue, 12 Feb 2019 15:29:50 +0100

Since printing of the printk buffer is now handled by the printk
kthread, minimize the console locking functions to just handle
locking of the console.

NOTE: With this console_flush_on_panic will no longer flush.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

22/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: track seq per console
Date: Tue, 12 Feb 2019 15:29:51 +0100

Allow each console to track which seq record was last printed. This
simplifies identifying dropped records.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

23/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: do boot_delay_msec inside printk_delay
Date: Tue, 12 Feb 2019 15:29:52 +0100

Both functions needed to be called one after the other, so just
integrate boot_delay_msec into printk_delay for simplification.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

24/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: print history for new consoles
Date: Tue, 12 Feb 2019 15:29:53 +0100

When new consoles register, they currently print how many messages
they have missed. However, many (or all) of those messages may still
be in the ring buffer. Add functionality to print as much of the
history as available. This is a clean replacement of the old
exclusive console hack.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

25/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: implement CON_PRINTBUFFER
Date: Tue, 12 Feb 2019 15:29:54 +0100

If the CON_PRINTBUFFER flag is not set, do not replay the history
for that console.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

26/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: add processor number to output
Date: Tue, 12 Feb 2019 15:29:55 +0100

It can be difficult to sort printk out if multiple processors are
printing simultaneously. Add the processor number to the printk
output to allow the messages to be sorted.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

27/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: console: add write_atomic interface
Date: Tue, 12 Feb 2019 15:29:56 +0100

Add a write_atomic callback to the console. This is an optional
function for console drivers. The function must be atomic (including
NMI safe) for writing to the console.

Console drivers must still implement the write callback. The
write_atomic callback will only be used for emergency messages.

Creating an NMI safe write_atomic that must synchronize with write
requires a careful implementation of the console driver. To aid with
the implementation, a set of console_atomic_* functions are provided:

    void console_atomic_lock(unsigned int *flags);
    void console_atomic_unlock(unsigned int flags);

These functions synchronize using the processor-reentrant cpu lock of
the printk buffer.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

28/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: introduce emergency messages
Date: Tue, 12 Feb 2019 15:29:57 +0100

Console messages are generally either critical or non-critical.
Critical messages are messages such as crashes or sysrq output.
Critical messages should never be lost because generally they provide
important debugging information.

Since all console messages are output via a fully preemptible printk
kernel thread, it is possible that messages are not output because
that thread cannot be scheduled (BUG in scheduler, run-away RT task,
etc).

To allow critical messages to be output independent of the
schedulability of the printk task, introduce an emergency mechanism
that _immediately_ outputs the message to the consoles. To avoid
possible unbounded latency issues, the emergency mechanism only
outputs the printk line provided by the caller and ignores any
pending messages in the log buffer.

Critical messages are identified as messages (by default) with log
level LOGLEVEL_WARNING or more critical. This is configurable via the
kernel option CONSOLE_LOGLEVEL_EMERGENCY.

Any messages output as emergency messages are skipped by the printk
thread on those consoles that output the emergency message.

In order for a console driver to support emergency messages, the
write_atomic function must be implemented by the driver. If not
implemented, the emergency messages are handled like all other
messages and are printed by the printk thread.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

29/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: serial: 8250: implement write_atomic
Date: Tue, 12 Feb 2019 15:29:58 +0100

Implement a non-sleeping NMI-safe write_atomic console function in
order to support emergency printk messages.

Since interrupts need to be disabled during transmit, all usage of
the IER register was wrapped with access functions that use the
console_atomic_lock function to synchronize register access while
tracking the state of the interrupts. This was necessary because
write_atomic is can be calling from an NMI context that has
preempted write_atomic.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

30/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: implement KERN_CONT
Date: Tue, 12 Feb 2019 15:29:59 +0100

Implement KERN_CONT based on the printing CPU rather than on the
printing task. As long as the KERN_CONT messages are coming from the
same CPU and no non-KERN_CONT messages come, the messages are assumed
to belong to each other.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

31/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: implement /dev/kmsg
Date: Tue, 12 Feb 2019 15:30:00 +0100

Since printk messages are now logged to a new ring buffer, update
the /dev/kmsg functions to pull the messages from there.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

32/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: implement syslog
Date: Tue, 12 Feb 2019 15:30:01 +0100

Since printk messages are now logged to a new ring buffer, update
the syslog functions to pull the messages from there.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

33/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: implement kmsg_dump
Date: Tue, 12 Feb 2019 15:30:02 +0100

Since printk messages are now logged to a new ring buffer, update
the kmsg_dump functions to pull the messages from there.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

34/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: remove unused code
Date: Tue, 12 Feb 2019 15:30:03 +0100

Code relating to the safe context and anything dealing with the
previous log buffer implementation is no longer in use. Remove it.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

35/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: set deferred to default loglevel, enforce mask
Date: Thu, 14 Feb 2019 23:13:30 +0100

All messages printed via vpritnk_deferred() were being
automatically treated as emergency messages.

Messages printed via vprintk_deferred() should be set to the
default loglevel. LOGLEVEL_SCHED is no longer relevant.

Also, enforce the loglevel mask for emergency messages.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

36/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: serial: 8250: remove that trylock in serial8250_console_write_atomic()
Date: Thu, 14 Feb 2019 17:38:24 +0100

This does not work as rtmutex in NMI context. As per John, it is not
needed.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

37/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: serial: 8250: export symbols which are used by symbols
Date: Sat, 16 Feb 2019 09:02:00 +0100

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

38/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: arm: remove printk_nmi_.*()
Date: Fri, 15 Feb 2019 14:34:20 +0100

It is no longer provided by the printk core code.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

39/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: only allow kernel to emergency message
Date: Sun, 17 Feb 2019 03:11:20 +0100

Emergency messages exist as a mechanism for the kernel to
communicate critical information to users. It is not meant for
use by userspace. Only allow facility=0 messages to be
processed by the emergency message code.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

40/298 [
Author: John Ogness
Email: john.ogness@linutronix.de
Subject: printk: devkmsg: llseek: reset clear if it is lost
Date: Fri, 22 Feb 2019 23:02:44 +0100

SEEK_DATA will seek to the last clear record. If this clear record
is no longer in the ring buffer, devkmsg_llseek() will go into an
infinite loop. Fix that by resetting the clear sequence if the old
clear record is no longer in the ring buffer.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

41/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: printk: print "rate-limitted" message as info
Date: Fri, 22 Feb 2019 12:47:13 +0100

If messages which are injected via kmsg are dropped then they don't need
to be printed as warnings. This is to avoid latency spikes if the
interface decides to print a lot of important messages.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

42/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: x86/ioapic: Don't let setaffinity unmask threaded EOI interrupt too early
Date: Tue, 17 Jul 2018 18:25:31 +0200

There is an issue with threaded interrupts which are marked ONESHOT
and using the fasteoi handler.

    if (IS_ONESHOT())
        mask_irq();

    ....
    ....

    cond_unmask_eoi_irq()
        chip->irq_eoi();

So if setaffinity is pending then the interrupt will be moved and then
unmasked, which is wrong as it should be kept masked up to the point where
the threaded handler finished. It's not a real problem, the interrupt will
just be able to fire before the threaded handler has finished, though the irq
masked state will be wrong for a bit.

The patch below should cure the issue. It also renames the horribly
misnomed functions so it becomes clear what they are supposed to do.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[bigeasy: add the body of the patch, use the same functions in both
          ifdef paths (spotted by Andy Shevchenko)]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

43/298 [
Author: Yang Shi
Email: yang.shi@linaro.org
Subject: arm: kprobe: replace patch_lock to raw lock
Date: Thu, 10 Nov 2016 16:17:55 -0800

When running kprobe on -rt kernel, the below bug is caught:

BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:931
in_atomic(): 1, irqs_disabled(): 128, pid: 14, name: migration/0
INFO: lockdep is turned off.
irq event stamp: 238
hardirqs last enabled at (237): [<80b5aecc>] _raw_spin_unlock_irqrestore+0x88/0x90
hardirqs last disabled at (238): [<80b56d88>] __schedule+0xec/0x94c
softirqs last enabled at (0): [<80225584>] copy_process.part.5+0x30c/0x1994
softirqs last disabled at (0): [< (null)>] (null)
Preemption disabled at:[<802f2b98>] cpu_stopper_thread+0xc0/0x140

CPU: 0 PID: 14 Comm: migration/0 Tainted: G O 4.8.3-rt2 #1
Hardware name: Freescale LS1021A
[<80212e7c>] (unwind_backtrace) from [<8020cd2c>] (show_stack+0x20/0x24)
[<8020cd2c>] (show_stack) from [<80689e14>] (dump_stack+0xa0/0xcc)
[<80689e14>] (dump_stack) from [<8025a43c>] (___might_sleep+0x1b8/0x2a4)
[<8025a43c>] (___might_sleep) from [<80b5b324>] (rt_spin_lock+0x34/0x74)
[<80b5b324>] (rt_spin_lock) from [<80b5c31c>] (__patch_text_real+0x70/0xe8)
[<80b5c31c>] (__patch_text_real) from [<80b5c3ac>] (patch_text_stop_machine+0x18/0x20)
[<80b5c3ac>] (patch_text_stop_machine) from [<802f2920>] (multi_cpu_stop+0xfc/0x134)
[<802f2920>] (multi_cpu_stop) from [<802f2ba0>] (cpu_stopper_thread+0xc8/0x140)
[<802f2ba0>] (cpu_stopper_thread) from [<802563a4>] (smpboot_thread_fn+0x1a4/0x354)
[<802563a4>] (smpboot_thread_fn) from [<80251d38>] (kthread+0x104/0x11c)
[<80251d38>] (kthread) from [<80207f70>] (ret_from_fork+0x14/0x24)

Since patch_text_stop_machine() is called in stop_machine() which disables IRQ,
sleepable lock should be not used in this atomic context, so replace patch_lock
to raw lock.

Signed-off-by: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

44/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: arm/unwind: use a raw_spin_lock
Date: Fri, 20 Sep 2013 14:31:54 +0200

Mostly unwind is done with irqs enabled however SLUB may call it with
irqs disabled while creating a new SLUB cache.

I had system freeze while loading a module which called
kmem_cache_create() on init. That means SLUB's __slab_alloc() disabled
interrupts and then

->new_slab_objects()
 ->new_slab()
  ->setup_object()
   ->setup_object_debug()
    ->init_tracking()
     ->set_track()
      ->save_stack_trace()
       ->save_stack_trace_tsk()
        ->walk_stackframe()
         ->unwind_frame()
          ->unwind_find_idx()
           =>spin_lock_irqsave(&unwind_lock);

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

45/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: cgroup: use irqsave in cgroup_rstat_flush_locked()
Date: Tue, 3 Jul 2018 18:19:48 +0200

All callers of cgroup_rstat_flush_locked() acquire cgroup_rstat_lock
either with spin_lock_irq() or spin_lock_irqsave().
cgroup_rstat_flush_locked() itself acquires cgroup_rstat_cpu_lock which
is a raw_spin_lock. This lock is also acquired in cgroup_rstat_updated()
in IRQ context and therefore requires _irqsave() locking suffix in
cgroup_rstat_flush_locked().
Since there is no difference between spin_lock_t and raw_spin_lock_t
on !RT lockdep does not complain here. On RT lockdep complains because
the interrupts were not disabled here and a deadlock is possible.

Acquire the raw_spin_lock_t with disabled interrupts.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

46/298 [
Author: Clark Williams
Email: williams@redhat.com
Subject: fscache: initialize cookie hash table raw spinlocks
Date: Tue, 3 Jul 2018 13:34:30 -0500

The fscache cookie mechanism uses a hash table of hlist_bl_head structures. The
PREEMPT_RT patcheset adds a raw spinlock to this structure and so on PREEMPT_RT
the structures get used uninitialized, causing warnings about bad magic numbers
when spinlock debugging is turned on.

Use the init function for fscache cookies.

Signed-off-by: Clark Williams <williams@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

47/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: Drivers: hv: vmbus: include header for get_irq_regs()
Date: Wed, 29 Aug 2018 21:59:04 +0200

On !RT the header file get_irq_regs() gets pulled in via other header files. On
RT it does not and the build fails:

    drivers/hv/vmbus_drv.c:975 implicit declaration of function ‘get_irq_regs’ [-Werror=implicit-function-declaration]
    drivers/hv/hv.c:115 implicit declaration of function ‘get_irq_regs’ [-Werror=implicit-function-declaration]

Add the header file for get_irq_regs() in a common header so it used by
vmbus_drv.c by hv.c for their get_irq_regs() usage.

Reported-by: Bernhard Landauer <oberon@manjaro.org>
Reported-by: Ralf Ramsauer <ralf.ramsauer@oth-regensburg.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

48/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: percpu: include irqflags.h for raw_local_irq_save()
Date: Thu, 11 Oct 2018 16:39:59 +0200

The header percpu.h header file is using raw_local_irq_save() but does
not include irqflags.h for its definition. It compiles because the
header file is included via an other header file.
On -RT the build fails because raw_local_irq_save() is not defined.

Include irqflags.h in percpu.h.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

49/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: mm: workingset: replace IRQ-off check with a lockdep assert.
Date: Mon, 11 Feb 2019 10:40:46 +0100

Commit

  68d48e6a2df57 ("mm: workingset: add vmstat counter for shadow nodes")

introduced an IRQ-off check to ensure that a lock is held which also
disabled interrupts. This does not work the same way on -RT because none
of the locks, that are held, disable interrupts.
Replace this check with a lockdep assert which ensures that the lock is
held.

Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

50/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: crypto: chtls: remove cdev_list_lock
Date: Mon, 11 Feb 2019 11:06:11 +0100

Last user of cdev_list_lock was removed in commit

  6422ccc5fbefb ("crypto/chelsio/chtls: listen fails with multiadapt")

Cc: Atul Gupta <atul.gupta@chelsio.com>
Cc: Harsh Jain <harsh@chelsio.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

51/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: crypto: user: remove crypto_cfg_mutex
Date: Mon, 11 Feb 2019 11:52:38 +0100

crypto_cfg_mutex was never used since it got introduced in commit

  cac5818c25d04 ("crypto: user - Implement a generic crypto statistics")

Cc: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

52/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: tpm: remove tpm_dev_wq_lock
Date: Mon, 11 Feb 2019 11:33:11 +0100

Added in commit

  9e1b74a63f776 ("tpm: add support for nonblocking operation")

but never actually used it.

Cc: Philip Tricca <philip.b.tricca@intel.com>
Cc: Tadeusz Struk <tadeusz.struk@intel.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

53/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Remove fpu->initialized usage in __fpu__restore_sig()
Date: Tue, 16 Oct 2018 11:08:14 +0200

This is a preparation for the removal of the ->initialized member in the
fpu struct.
__fpu__restore_sig() is deactivating the FPU via fpu__drop() and then
setting manually ->initialized followed by fpu__restore(). The result is
that it is possible to manipulate fpu->state and the state of registers
won't be saved/restored on a context switch which would overwrite
fpu->state.

Don't access the fpu->state while the content is read from user space
and examined / sanitized. Use a temporary kmalloc() buffer for the
preparation of the FPU registers and once the state is considered okay,
load it. Should something go wrong, return with an error and without
altering the original FPU registers.

The removal of "fpu__initialize()" is a nop because fpu->initialized is
already set for the user task.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Borislav Petkov <bp@suse.de>
]

54/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Remove fpu__restore()
Date: Wed, 17 Oct 2018 16:10:45 +0200

There are no users of fpu__restore() so it is time to remove it.
The comment regarding fpu__restore() and TS bit is stale since commit
  b3b0870ef3ffe ("i387: do not preload FPU state at task switch time")
and has no meaning since.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

55/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Remove preempt_disable() in fpu__clear()
Date: Wed, 17 Oct 2018 14:58:28 +0200

The preempt_disable() section was introduced in commit

  a10b6a16cdad8 ("x86/fpu: Make the fpu state change in fpu__clear() scheduler-atomic")

and it was said to be temporary.

fpu__initialize() initializes the FPU struct to its "init" value and
then sets ->initialized to 1. The last part is the important one.
The content of the `state' does not matter because it gets set via
copy_init_fpstate_to_fpregs().
A preemption here has little meaning because the registers will always be
set to the same content after copy_init_fpstate_to_fpregs(). A softirq
with a kernel_fpu_begin() could also force to save FPU's registers after
fpu__initialize() without changing the outcome here.

Remove the preempt_disable() section in fpu__clear(), preemption here
does not hurt.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
]

56/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Always init the `state' in fpu__clear()
Date: Wed, 17 Oct 2018 15:27:34 +0200

fpu__clear() only initializes the `state' if the FPU is present. This
initialisation is also required for the FPU-less system and takes place
in math_emulate(). Since fpu__initialize() only performs the
initialization if ->initialized is zero it does not matter that it is
invoked each time an opcode is emulated. It makes the removal of
->initialized easier if the struct is also initialized in the FPU-less
case at the same time.

Move fpu__initialize() before the FPU check so it is also performed in
the FPU-less case.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
]

57/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Remove fpu->initialized usage in copy_fpstate_to_sigframe()
Date: Fri, 19 Oct 2018 16:57:14 +0200

With lazy-FPU support the (now named variable) ->initialized was set to true if
the CPU's FPU registers were holding the a valid state of the FPU registers for
the active process. If it was set to false then the FPU state was saved in
fpu->state and the FPU was deactivated.
With lazy-FPU gone, ->initialized is always true for user threads and kernel
threads never this function so ->initialized is always true in
copy_fpstate_to_sigframe().
The using_compacted_format() check is also a leftover from the lazy-FPU time.
In the `->initialized == false' case copy_to_user() would copy the compacted
buffer while userland would expect the non-compacted format instead. So in
order to save the FPU state in the non-compacted form it issues the xsave
opcode to save the *current* FPU state.
The FPU is not enabled so the attempt raises the FPU trap, the trap restores
the FPU content and re-enables the FPU and the xsave opcode is invoked again and
succeeds. *This* does not longer work since commit

  bef8b6da9522 ("x86/fpu: Handle #NM without FPU emulation as an error")

Remove check for ->initialized because it is always true and remove the
false condition. Update the comment to reflect that the "state is always live".

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

58/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Don't save fxregs for ia32 frames in copy_fpstate_to_sigframe()
Date: Tue, 27 Nov 2018 13:08:50 +0100

In commit

  72a671ced66db ("x86, fpu: Unify signal handling code paths for x86 and x86_64 kernels")

the 32bit and 64bit path of the signal delivery code were merged. The 32bit version:
|int save_i387_xstate_ia32(void __user *buf)
|…
|       if (cpu_has_xsave)
|               return save_i387_xsave(fp);
|       if (cpu_has_fxsr)
|               return save_i387_fxsave(fp);

The 64bit version:
|int save_i387_xstate(void __user *buf)
|…
|       if (user_has_fpu()) {
|               if (use_xsave())
|                       err = xsave_user(buf);
|               else
|                       err = fxsave_user(buf);
|
|               if (unlikely(err)) {
|                       __clear_user(buf, xstate_size);
|                       return err;

The merge:
|int save_xstate_sig(void __user *buf, void __user *buf_fx, int size)
|…
|       if (user_has_fpu()) {
|               /* Save the live register state to the user directly. */
|               if (save_user_xstate(buf_fx))
|                       return -1;
|               /* Update the thread's fxstate to save the fsave header. */
|               if (ia32_fxstate)
|                       fpu_fxsave(&tsk->thread.fpu);

I don't think that we needed to save the FPU registers to ->thread.fpu because
the registers were stored in `buf_fx'. Today the state will be restored from
`buf_fx' after the signal was handled (I assume that this was also the case
with lazy-FPU). Since commit

  66463db4fc560 ("x86, fpu: shift drop_init_fpu() from save_xstate_sig() to handle_signal()")

it is ensured that the signal handler starts with clear/fresh set of FPU
registers which means that the previous store is futile.

Remove copy_fxregs_to_kernel() because task's FPU state is cleared later in
handle_signal() via fpu__clear().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

59/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Remove fpu->initialized
Date: Wed, 17 Oct 2018 18:08:35 +0200

The `initialized' member of the fpu struct is always set to one for user
tasks and zero for kernel tasks. This avoids saving/restoring the FPU
registers for kernel threads.

The ->initialized = 0 case for user tasks has been removed in previous changes
for instance by always an explicit init at fork() time for FPU-less system which
was otherwise delayed until the emulated opcode.

The context switch code (switch_fpu_prepare() + switch_fpu_finish())
can't unconditionally save/restore registers for kernel threads. Not only would
it slow down switch but also load a zeroed xcomp_bv for the XSAVES.

For kernel_fpu_begin() (+end) the situation is similar: EFI with runtime
services uses this before alternatives_patched is true. Which means that this
function is used too early and it wasn't the case before.

For those two cases current->mm is used to determine between user &
kernel thread. For kernel_fpu_begin() we skip save/restore of the FPU
registers.
During the context switch into a kernel thread we don't do anything.
There is no reason to save the FPU state of a kernel thread.
The reordering in __switch_to() is important because the current() pointer
needs to be valid before switch_fpu_finish() is invoked so ->mm is seen of the
new task instead the old one.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

60/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Remove user_fpu_begin()
Date: Thu, 18 Oct 2018 18:34:11 +0200

user_fpu_begin() sets fpu_fpregs_owner_ctx to task's fpu struct. This is
always the case since there is no lazy FPU anymore.

fpu_fpregs_owner_ctx is used during context switch to decide if it needs
to load the saved registers or if the currently loaded registers are
valid. It could be skipped during
	taskA -> kernel thread -> taskA

because the switch to kernel thread would not alter the CPU's FPU state.

Since this field is always updated during context switch and never
invalidated, setting it manually (in user context) makes no difference.
A kernel thread with kernel_fpu_begin() block could set
fpu_fpregs_owner_ctx to NULL but a kernel thread does not use
user_fpu_begin().
This is a leftover from the lazy-FPU time.

Remove user_fpu_begin(), it does not change fpu_fpregs_owner_ctx's
content.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
]

61/298 [
Author: Rik van Riel
Email: riel@surriel.com
Subject: x86/fpu: Add (__)make_fpregs_active helpers
Date: Sun, 9 Sep 2018 18:30:45 +0200

Add helper function that ensures the floating point registers for
the current task are active. Use with preemption disabled.

Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

62/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Make __raw_xsave_addr() use feature number instead of mask
Date: Tue, 2 Oct 2018 10:28:15 +0200

Most users of __raw_xsave_addr() use a feature number, shift it to a
mask and then __raw_xsave_addr() shifts it back to the feature number.

Make __raw_xsave_addr() use the feature number as an argument.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
]

63/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Make get_xsave_field_ptr() and get_xsave_addr() use feature number instead of mask
Date: Thu, 18 Oct 2018 12:58:06 +0200

After changing the argument of __raw_xsave_addr() from a mask to number
Dave suggested to check if it makes sense to do the same for
get_xsave_addr(). As it turns out it does. Only get_xsave_addr() needs
the mask to check if the requested feature is part of what is
support/saved and then uses the number again. The shift operation is
cheaper compared to "find last bit set". Also, the feature number uses
less opcode space compared to the mask :)

Make get_xsave_addr() argument a xfeature number instead of mask and fix
up its callers.
As part of this use xfeature_nr and xfeature_mask consistently.
This results in changes to the kvm code as:
	feature -> xfeature_mask
	index -> xfeature_nr

Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

64/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Only write PKRU if it is different from current
Date: Fri, 19 Oct 2018 12:46:53 +0200

Dave Hansen says that the `wrpkru' is more expensive than `rdpkru'. It
has a higher cycle cost and it's also practically a (light) speculation
barrier.

As an optimisation read the current PKRU value and only write the new
one if it is different.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

65/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/pkeys: Don't check if PKRU is zero before writting it
Date: Fri, 19 Oct 2018 13:59:26 +0200

write_pkru() checks if the current value is the same as the expected
value. So instead just checking if the current and new value is zero
(and skip the write in such a case) we can benefit from that.

Remove the zero check of PKRU, write_pkru() provides a similar check.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

66/298 [
Author: Rik van Riel
Email: riel@surriel.com
Subject: x86/fpu: Eager switch PKRU state
Date: Sun, 9 Sep 2018 18:30:47 +0200

While most of a task's FPU state is only needed in user space, the
protection keys need to be in place immediately after a context switch.

The reason is that any access to userspace memory while running in
kernel mode also need to abide by the memory permissions specified in
the protection keys.

The "eager switch" is a preparation for loading the FPU state on return
to userland. Instead of decoupling PKRU state from xstate I update PKRU
within xstate on write operations by the kernel.

The read/write_pkru() is moved to another header file so it can easily
accessed from pgtable.h and fpu/internal.h.

For user tasks we should always get the PKRU from the xsave area and it
should not change anything because the PKRU value was loaded as part of
FPU restore.
For kernel kernel threads we now will have the default "allow
everything" written.  Before this commit the kernel thread would end up
with a random value which it inherited from the previous user task.

Signed-off-by: Rik van Riel <riel@surriel.com>
[bigeasy: save pkru to xstate, no cache, don't use __raw_xsave_addr()]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

67/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/entry: Add TIF_NEED_FPU_LOAD
Date: Wed, 5 Sep 2018 18:34:47 +0200

Add TIF_NEED_FPU_LOAD. This is reserved for loading the FPU registers
before returning to userland. This flag must not be set for systems
without a FPU.
If this flag is cleared, the CPU's FPU register hold the current content
of current()'s FPU register. The in-memory copy (union fpregs_state) is
not valid.
If this flag is set, then all of CPU's FPU register may hold a random
value (except for PKRU) and it is required to load the content of the
FPU register on return to userland.

It is introduced now, so we can add code handling it now before adding
the main feature.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

68/298 [
Author: Rik van Riel
Email: riel@surriel.com
Subject: x86/fpu: Always store the registers in copy_fpstate_to_sigframe()
Date: Sun, 9 Sep 2018 18:30:50 +0200

copy_fpstate_to_sigframe() stores the registers directly to user space.
This is okay because the FPU register are valid and saving it directly
avoids saving it into kernel memory and making a copy.
However… We can't keep doing this if we are going to restore the FPU
registers on the return to userland. It is possible that the FPU
registers will be invalidated in the middle of the save operation and
this should be done with disabled preemption / BH.

Save the FPU registers to task's FPU struct and copy them to the user
memory later on.

This code is extracted from an earlier version of the patchset while
there still was lazy-FPU on x86.

Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

69/298 [
Author: Rik van Riel
Email: riel@surriel.com
Subject: x86/fpu: Prepare copy_fpstate_to_sigframe() for TIF_NEED_FPU_LOAD
Date: Sun, 9 Sep 2018 18:30:51 +0200

The FPU registers need only to be saved if TIF_NEED_FPU_LOAD is not set.
Otherwise this has been already done and can be skipped.

Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

70/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Update xstate's PKRU value on write_pkru()
Date: Fri, 19 Oct 2018 23:50:27 +0200

During the context switch the xstate is loaded which also includes the
PKRU value.
If xstate is restored on return to userland it is required that the
PKRU value in xstate is the same as the one in the CPU.

Save the PKRU in xstate during modification.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

71/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Inline copy_user_to_fpregs_zeroing()
Date: Wed, 7 Nov 2018 15:06:06 +0100

Start refactoring __fpu__restore_sig() by inlining
copy_user_to_fpregs_zeroing().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

72/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Let __fpu__restore_sig() restore the !32bit+fxsr frame from kernel memory
Date: Tue, 27 Nov 2018 17:48:32 +0100

The !32bit+fxsr case loads the new state from user memory. In case we
restore the FPU state on return to userland we can't do this. It would
be required to disable preemption in order to avoid a context switch
which would set TIF_NEED_FPU_LOAD. If this happens before the "restore"
operation then the loaded registers would become volatile.

Disabling preemption while accessing user memory requires to disable the
pagefault handler. An error during XRSTOR would then mean that either a
page fault occured (and we have to retry with enabled page fault
handler) or a #GP occured because the xstate is bogus (after all the
sig-handler can modify it).

In order to avoid that mess, copy the FPU state from userland, validate
it and then load it. The copy_users_…() helper are basically the old
helper except that they operate on kernel memory and the fault handler
just sets the error value and the caller handles it.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

73/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/fpu: Merge the two code paths in __fpu__restore_sig()
Date: Tue, 27 Nov 2018 21:08:01 +0100

The ia32_fxstate case (32bit with fxsr) and the other (64bit, 32bit
without fxsr) restore both from kernel memory and sanitize the content.
The !ia32_fxstate version restores missing xstates from "init state"
while the ia32_fxstate doesn't and skips it.

Merge the two code paths and keep the !ia32_fxstate version. Copy only
the user_i387_ia32_struct data structure in the ia32_fxstate.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

74/298 [
Author: Rik van Riel
Email: riel@surriel.com
Subject: x86/fpu: Defer FPU state load until return to userspace
Date: Sun, 9 Sep 2018 18:30:53 +0200

Defer loading of FPU state until return to userspace. This gives
the kernel the potential to skip loading FPU state for tasks that
stay in kernel mode, or for tasks that end up with repeated
invocations of kernel_fpu_begin() & kernel_fpu_end().

The __fpregs_changes_{begin|end}() section ensures that the register
remain unchanged. Otherwise a context switch or a BH could save the
registers to its FPU context and processor's FPU register would became
random if beeing modified at the same time.

KVM swaps the host/guest register on entry/exit path. I kept the flow as
is. First it ensures that the registers are loaded and then saves the
current (host) state before it loads the guest's register. The swap is
done at the very end with disabled interrupts so it should not change
anymore before theg guest is entered. The read/save version seems to be
cheaper compared to memcpy() in a micro benchmark.

Each thread gets TIF_NEED_FPU_LOAD set as part of fork() / fpu__copy().
For kernel threads, this flag gets never cleared which avoids saving /
restoring the FPU state for kernel threads and during in-kernel usage of
the FPU register.

Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

75/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: efi: Allow efi=runtime
Date: Thu, 26 Jul 2018 15:06:10 +0200

In case the option "efi=noruntime" is default at built-time, the user
could overwrite its sate by `efi=runtime' and allow it again.

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

76/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: drm/i915/fence: Do not use TIMER_IRQSAFE
Date: Tue, 12 Feb 2019 12:45:19 +0100

The timer is initialized with TIMER_IRQSAFE flag. It does look like the
timer callback requires this flag at all. Its sole purpose is to ensure
synchronisation in the workqueue code.

Remove TIMER_IRQSAFE flag because it is not required.

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

77/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: kthread: Do not use TIMER_IRQSAFE
Date: Tue, 12 Feb 2019 12:57:45 +0100

The TIMER_IRQSAFE was introduced in commit

  22597dc3d97b1 ("kthread: initial support for delayed kthread work")

which modelled the delayed kthread code after workqueue's code. The
workqueue code requires the flag TIMER_IRQSAFE for synchronisation
purpose. This is not true for kthread's delay timer since all
operations occur under a lock.

Remove TIMER_IRQSAFE from the timer initialisation.
Use timer_setup() for initialisation purpose which is the official
function.

Cc: Petr Mladek <pmladek@suse.com>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

78/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: arm64: KVM: compute_layout before altenates are applied
Date: Thu, 26 Jul 2018 09:13:42 +0200

compute_layout() is invoked as part of an alternative fixup under
stop_machine() and needs a sleeping lock as part of get_random_long().

Invoke compute_layout() before the alternatives are applied.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

79/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: of: allocate / free phandle cache outside of the devtree_lock
Date: Fri, 31 Aug 2018 14:16:30 +0200

The phandle cache code allocates memory while holding devtree_lock which
is a raw_spinlock_t. Memory allocation (and free()) is not possible on
RT while a raw_spinlock_t is held.
Invoke the kfree() and kcalloc() while the lock is dropped.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: devicetree@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

80/298 [
Author: Paul E. McKenney
Email: paulmck@linux.ibm.com
Subject: EXP rcu: skip the workqueue path on RT
Date: Mon, 29 Oct 2018 11:53:01 +0100

The function sync_rcu_exp_select_cpus() is only invoked once on boot because
the "force expedite" is not enabled on RT. In that case on RT we have like we
wouldn't have workqueues available so that we don't attempt to schedule them
with disabled preemption.

Suggested-by: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

81/298 [
Author: He Zhe
Email: zhe.he@windriver.com
Subject: kmemleak: Turn kmemleak_lock to raw spinlock on RT
Date: Wed, 19 Dec 2018 16:30:57 +0100

kmemleak_lock, as a rwlock on RT, can possibly be held in atomic context and
causes the follow BUG.

BUG: scheduling while atomic: migration/15/132/0x00000002
Preemption disabled at:
[<ffffffff8c927c11>] cpu_stopper_thread+0x71/0x100
CPU: 15 PID: 132 Comm: migration/15 Not tainted 4.19.0-rt1-preempt-rt #1
Call Trace:
 schedule+0x3d/0xe0
 __rt_spin_lock+0x26/0x30
 __write_rt_lock+0x23/0x1a0
 rt_write_lock+0x2a/0x30
 find_and_remove_object+0x1e/0x80
 delete_object_full+0x10/0x20
 kmemleak_free+0x32/0x50
 kfree+0x104/0x1f0
 intel_pmu_cpu_dying+0x67/0x70
 x86_pmu_dying_cpu+0x1a/0x30
 cpuhp_invoke_callback+0x92/0x700
 take_cpu_down+0x70/0xa0
 multi_cpu_stop+0x62/0xc0
 cpu_stopper_thread+0x79/0x100
 smpboot_thread_fn+0x20f/0x2d0
 kthread+0x121/0x140

And on v4.18 stable tree the following call trace, caused by grabbing
kmemleak_lock again, is also observed.

kernel BUG at kernel/locking/rtmutex.c:1048!
CPU: 5 PID: 689 Comm: mkfs.ext4 Not tainted 4.18.16-rt9-preempt-rt #1
Call Trace:
 rt_write_lock+0x2a/0x30
 create_object+0x17d/0x2b0
 kmemleak_alloc+0x34/0x50
 kmem_cache_alloc+0x146/0x220
 mempool_alloc_slab+0x15/0x20
 mempool_alloc+0x65/0x170
 sg_pool_alloc+0x21/0x60
 sg_alloc_table_chained+0x8b/0xb0
…
 blk_flush_plug_list+0x204/0x230
 schedule+0x87/0xe0
 rt_write_lock+0x2a/0x30
 create_object+0x17d/0x2b0
 kmemleak_alloc+0x34/0x50
 __kmalloc_node+0x1cd/0x340
 alloc_request_size+0x30/0x70
 mempool_alloc+0x65/0x170
 get_request+0x4e3/0x8d0
 blk_queue_bio+0x153/0x470
 generic_make_request+0x1dc/0x3f0
 submit_bio+0x49/0x140
…

kmemleak is an error detecting feature. We would not expect as good performance
as without it. As there is no raw rwlock defining helpers, we turn kmemleak_lock
to a raw spinlock.

Signed-off-by: He Zhe <zhe.he@windriver.com>
Cc: catalin.marinas@arm.com
Cc: bigeasy@linutronix.de
Cc: tglx@linutronix.de
Cc: rostedt@goodmis.org
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lkml.kernel.org/r/1542877459-144382-1-git-send-email-zhe.he@windriver.com
Link: https://lkml.kernel.org/r/20181218150744.GB20197@arrakis.emea.arm.com


Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

82/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: NFSv4: replace seqcount_t with a seqlock_t
Date: Fri, 28 Oct 2016 23:05:11 +0200

The raw_write_seqcount_begin() in nfs4_reclaim_open_state() bugs me
because it maps to preempt_disable() in -RT which I can't have at this
point. So I took a look at the code.
It the lockdep part was removed in commit abbec2da13f0 ("NFS: Use
raw_write_seqcount_begin/end int nfs4_reclaim_open_state") because
lockdep complained. The whole seqcount thing was introduced in commit
c137afabe330 ("NFSv4: Allow the state manager to mark an open_owner as
being recovered").
The recovery threads runs only once.
write_seqlock() does not work on !RT because it disables preemption and it the
writer side is preemptible (has to remain so despite the fact that it will
block readers).

Reported-by: kernel test robot <xiaolong.ye@intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

83/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: kernel: sched: Provide a pointer to the valid CPU mask
Date: Tue, 4 Apr 2017 12:50:16 +0200

In commit 4b53a3412d66 ("sched/core: Remove the tsk_nr_cpus_allowed()
wrapper") the tsk_nr_cpus_allowed() wrapper was removed. There was not
much difference in !RT but in RT we used this to implement
migrate_disable(). Within a migrate_disable() section the CPU mask is
restricted to single CPU while the "normal" CPU mask remains untouched.

As an alternative implementation Ingo suggested to use
	struct task_struct {
		const cpumask_t		*cpus_ptr;
		cpumask_t		cpus_mask;
        };
with
	t->cpus_allowed_ptr = &t->cpus_allowed;

In -RT we then can switch the cpus_ptr to
	t->cpus_allowed_ptr = &cpumask_of(task_cpu(p));

in a migration disabled region. The rules are simple:
- Code that 'uses' ->cpus_allowed would use the pointer.
- Code that 'modifies' ->cpus_allowed would use the direct mask.

While converting the existing users I tried to stick with the rules
above however… well mostly CPUFREQ tries to temporary switch the CPU
mask to do something on a certain CPU and then switches the mask back it
its original value. So in theory `cpus_ptr' could or should be used.
However if this is invoked in a migration disabled region (which is not
the case because it would require something like preempt_disable() and
set_cpus_allowed_ptr() might sleep so it can't be) then the "restore"
part would restore the wrong mask. So it only looks strange and I go for
the pointer…

Some drivers copy the cpumask without cpumask_copy() and others use
cpumask_copy but without alloc_cpumask_var(). I did not fix those as
part of this, could do this as a follow up…

So is this the way we want it?
Is the usage of `cpus_ptr' vs `cpus_mask' for the set + restore part
(see cpufreq users) what we want? At some point it looks like they
should use a different interface for their doing. I am not sure why
switching to certain CPU is important but maybe it could be done via a
workqueue from the CPUFREQ core (so we have a comment desribing why are
doing this and a get_online_cpus() to ensure that the CPU does not go
offline too early).

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

84/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: kernel/sched/core: add migrate_disable()
Date: Sat, 27 May 2017 19:02:06 +0200

]

85/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: sched/migrate_disable: Add export_symbol_gpl for __migrate_disabled
Date: Tue, 9 Oct 2018 17:34:50 +0200

Jonathan reported that lttng/modules can't use __migrate_disabled().
This function is only used by sched/core itself and the tracing
infrastructure to report the migrate counter (lttng does probably the
same). Since the rework migrate_disable() it moved from sched.h to
preempt.h and is became an exported function instead of a "static
inline" due to the header recursion of preempt vs sched.

Since the compiler inlines the function for sched/core usage, add a
EXPORT_SYMBOL_GPL to allow the module/LTTNG usage.

Reported-by: Jonathan Rajott <jonathan.rajotte-julien@efficios.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

86/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: arm: at91: do not disable/enable clocks in a row
Date: Wed, 9 Mar 2016 10:51:06 +0100

Currently the driver will disable the clock and enable it one line later
if it is switching from periodic mode into one shot.
This can be avoided and causes a needless warning on -RT.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

87/298 [
Author: Benedikt Spranger
Email: b.spranger@linutronix.de
Subject: clocksource: TCLIB: Allow higher clock rates for clock events
Date: Mon, 8 Mar 2010 18:57:04 +0100

As default the TCLIB uses the 32KiHz base clock rate for clock events.
Add a compile time selection to allow higher clock resulution.

(fixed up by Sami Pietikäinen <Sami.Pietikainen@wapice.com>)

Signed-off-by: Benedikt Spranger <b.spranger@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

88/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: timekeeping: Split jiffies seqlock
Date: Thu, 14 Feb 2013 22:36:59 +0100

Replace jiffies_lock seqlock with a simple seqcounter and a rawlock so
it can be taken in atomic context on RT.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

89/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: signal: Revert ptrace preempt magic
Date: Wed, 21 Sep 2011 19:57:12 +0200

Upstream commit '53da1d9456fe7f8 fix ptrace slowness' is nothing more
than a bandaid around the ptrace design trainwreck. It's not a
correctness issue, it's merily a cosmetic bandaid.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

90/298 [
Author: Marc Kleine-Budde
Email: mkl@pengutronix.de
Subject: net: sched: Use msleep() instead of yield()
Date: Wed, 5 Mar 2014 00:49:47 +0100

On PREEMPT_RT enabled systems the interrupt handler run as threads at prio 50
(by default). If a high priority userspace process tries to shut down a busy
network interface it might spin in a yield loop waiting for the device to
become idle. With the interrupt thread having a lower priority than the
looping process it might never be scheduled and so result in a deadlock on UP
systems.

With Magic SysRq the following backtrace can be produced:

> test_app R running      0   174    168 0x00000000
> [<c02c7070>] (__schedule+0x220/0x3fc) from [<c02c7870>] (preempt_schedule_irq+0x48/0x80)
> [<c02c7870>] (preempt_schedule_irq+0x48/0x80) from [<c0008fa8>] (svc_preempt+0x8/0x20)
> [<c0008fa8>] (svc_preempt+0x8/0x20) from [<c001a984>] (local_bh_enable+0x18/0x88)
> [<c001a984>] (local_bh_enable+0x18/0x88) from [<c025316c>] (dev_deactivate_many+0x220/0x264)
> [<c025316c>] (dev_deactivate_many+0x220/0x264) from [<c023be04>] (__dev_close_many+0x64/0xd4)
> [<c023be04>] (__dev_close_many+0x64/0xd4) from [<c023be9c>] (__dev_close+0x28/0x3c)
> [<c023be9c>] (__dev_close+0x28/0x3c) from [<c023f7f0>] (__dev_change_flags+0x88/0x130)
> [<c023f7f0>] (__dev_change_flags+0x88/0x130) from [<c023f904>] (dev_change_flags+0x10/0x48)
> [<c023f904>] (dev_change_flags+0x10/0x48) from [<c024c140>] (do_setlink+0x370/0x7ec)
> [<c024c140>] (do_setlink+0x370/0x7ec) from [<c024d2f0>] (rtnl_newlink+0x2b4/0x450)
> [<c024d2f0>] (rtnl_newlink+0x2b4/0x450) from [<c024cfa0>] (rtnetlink_rcv_msg+0x158/0x1f4)
> [<c024cfa0>] (rtnetlink_rcv_msg+0x158/0x1f4) from [<c0256740>] (netlink_rcv_skb+0xac/0xc0)
> [<c0256740>] (netlink_rcv_skb+0xac/0xc0) from [<c024bbd8>] (rtnetlink_rcv+0x18/0x24)
> [<c024bbd8>] (rtnetlink_rcv+0x18/0x24) from [<c02561b8>] (netlink_unicast+0x13c/0x198)
> [<c02561b8>] (netlink_unicast+0x13c/0x198) from [<c025651c>] (netlink_sendmsg+0x264/0x2e0)
> [<c025651c>] (netlink_sendmsg+0x264/0x2e0) from [<c022af98>] (sock_sendmsg+0x78/0x98)
> [<c022af98>] (sock_sendmsg+0x78/0x98) from [<c022bb50>] (___sys_sendmsg.part.25+0x268/0x278)
> [<c022bb50>] (___sys_sendmsg.part.25+0x268/0x278) from [<c022cf08>] (__sys_sendmsg+0x48/0x78)
> [<c022cf08>] (__sys_sendmsg+0x48/0x78) from [<c0009320>] (ret_fast_syscall+0x0/0x2c)

This patch works around the problem by replacing yield() by msleep(1), giving
the interrupt thread time to finish, similar to other changes contained in the
rt patch set. Using wait_for_completion() instead would probably be a better
solution.

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

91/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rt: Provide PREEMPT_RT_BASE config switch
Date: Fri, 17 Jun 2011 12:39:57 +0200

Introduce PREEMPT_RT_BASE which enables parts of
PREEMPT_RT_FULL. Forces interrupt threading and enables some of the RT
substitutions for testing.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

92/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: cpumask: Disable CONFIG_CPUMASK_OFFSTACK for RT
Date: Wed, 14 Dec 2011 01:03:49 +0100

There are "valid" GFP_ATOMIC allocations such as

|BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:931
|in_atomic(): 1, irqs_disabled(): 0, pid: 2130, name: tar
|1 lock held by tar/2130:
| #0:  (&mm->mmap_sem){++++++}, at: [<ffffffff811d4e89>] SyS_brk+0x39/0x190
|Preemption disabled at:[<ffffffff81063048>] flush_tlb_mm_range+0x28/0x350
|
|CPU: 1 PID: 2130 Comm: tar Tainted: G        W       4.8.2-rt2+ #747
|Call Trace:
| [<ffffffff814d52dc>] dump_stack+0x86/0xca
| [<ffffffff810a26fb>] ___might_sleep+0x14b/0x240
| [<ffffffff819bc1d4>] rt_spin_lock+0x24/0x60
| [<ffffffff81194fba>] get_page_from_freelist+0x83a/0x11b0
| [<ffffffff81195e8b>] __alloc_pages_nodemask+0x15b/0x1190
| [<ffffffff811f0b81>] alloc_pages_current+0xa1/0x1f0
| [<ffffffff811f7df5>] new_slab+0x3e5/0x690
| [<ffffffff811fb0d5>] ___slab_alloc+0x495/0x660
| [<ffffffff811fb311>] __slab_alloc.isra.79+0x71/0xc0
| [<ffffffff811fb447>] __kmalloc_node+0xe7/0x240
| [<ffffffff814d4ee0>] alloc_cpumask_var_node+0x20/0x50
| [<ffffffff814d4f3e>] alloc_cpumask_var+0xe/0x10
| [<ffffffff810430c1>] native_send_call_func_ipi+0x21/0x130
| [<ffffffff8111c13f>] smp_call_function_many+0x22f/0x370
| [<ffffffff81062b64>] native_flush_tlb_others+0x1a4/0x3a0
| [<ffffffff8106309b>] flush_tlb_mm_range+0x7b/0x350
| [<ffffffff811c88e2>] tlb_flush_mmu_tlbonly+0x62/0xd0
| [<ffffffff811c9af4>] tlb_finish_mmu+0x14/0x50
| [<ffffffff811d1c84>] unmap_region+0xe4/0x110
| [<ffffffff811d3db3>] do_munmap+0x293/0x470
| [<ffffffff811d4f8c>] SyS_brk+0x13c/0x190
| [<ffffffff810032e2>] do_fast_syscall_32+0xb2/0x2f0
| [<ffffffff819be181>] entry_SYSENTER_compat+0x51/0x60

which forbid allocations at run-time.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

93/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: jump-label: disable if stop_machine() is used
Date: Wed, 8 Jul 2015 17:14:48 +0200

Some architectures are using stop_machine() while switching the opcode which
leads to latency spikes.
The architectures which use stop_machine() atm:
- ARM stop machine
- s390 stop machine

The architecures which use other sorcery:
- MIPS
- X86
- powerpc
- sparc
- arm64

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[bigeasy: only ARM for now]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

94/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: kconfig: Disable config options which are not RT compatible
Date: Sun, 24 Jul 2011 12:11:43 +0200

Disable stuff which is known to have issues on RT

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

95/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: lockdep: disable self-test
Date: Tue, 17 Oct 2017 16:36:18 +0200

The self-test wasn't always 100% accurate for RT. We disabled a few
tests which failed because they had a different semantic for RT. Some
still reported false positives. Now the selftest locks up the system
during boot and it needs to be investigated…

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

96/298 [
Author: Ingo Molnar
Email: mingo@elte.hu
Subject: mm: Allow only slub on RT
Date: Fri, 3 Jul 2009 08:44:03 -0500

Disable SLAB and SLOB on -RT. Only SLUB is adopted to -RT needs.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

97/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: locking: Disable spin on owner for RT
Date: Sun, 17 Jul 2011 21:51:45 +0200

Drop spin on owner for mutex / rwsem. We are most likely not using it
but…

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

98/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rcu: Disable RCU_FAST_NO_HZ on RT
Date: Sun, 28 Oct 2012 13:26:09 +0000

This uses a timer_list timer from the irq disabled guts of the idle
code. Disable it for now to prevent wreckage.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

99/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: rcu: make RCU_BOOST default on RT
Date: Fri, 21 Mar 2014 20:19:05 +0100

Since it is no longer invoked from the softirq people run into OOM more
often if the priority of the RCU thread is too low. Making boosting
default on RT should help in those case and it can be switched off if
someone knows better.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

100/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: sched: Disable CONFIG_RT_GROUP_SCHED on RT
Date: Mon, 18 Jul 2011 17:03:52 +0200

Carsten reported problems when running:

  taskset 01 chrt -f 1 sleep 1

from within rc.local on a F15 machine. The task stays running and
never gets on the run queue because some of the run queues have
rt_throttled=1 which does not go away. Works nice from a ssh login
shell. Disabling CONFIG_RT_GROUP_SCHED solves that as well.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

101/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: net/core: disable NET_RX_BUSY_POLL
Date: Sat, 27 May 2017 19:02:06 +0200

sk_busy_loop() does preempt_disable() followed by a few operations which can
take sleeping locks and may get long.
I _think_ that we could use preempt_disable_nort() (in sk_busy_loop()) instead
but after a successfull cmpxchg(&napi->state, …) we would gain the ressource
and could be scheduled out. At this point nobody knows who (which context) owns
it and so it could take a while until the state is realeased and napi_poll()
could be invoked again.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

102/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: arm*: disable NEON in kernel mode
Date: Fri, 1 Dec 2017 10:42:03 +0100

NEON in kernel mode is used by the crypto algorithms and raid6 code.
While the raid6 code looks okay, the crypto algorithms do not: NEON
is enabled on first invocation and may allocate/free/map memory before
the NEON mode is disabled again.
This needs to be changed until it can be enabled.
On ARM NEON in kernel mode can be simply disabled. on ARM64 it needs to
stay on due to possible EFI callbacks so here I disable each algorithm.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

103/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: powerpc: Use generic rwsem on RT
Date: Tue, 14 Jul 2015 14:26:34 +0200

Use generic code which uses rtmutex

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

104/298 [
Author: Bogdan Purcareata
Email: bogdan.purcareata@freescale.com
Subject: powerpc/kvm: Disable in-kernel MPIC emulation for PREEMPT_RT_FULL
Date: Fri, 24 Apr 2015 15:53:13 +0000

While converting the openpic emulation code to use a raw_spinlock_t enables
guests to run on RT, there's still a performance issue. For interrupts sent in
directed delivery mode with a multiple CPU mask, the emulated openpic will loop
through all of the VCPUs, and for each VCPUs, it call IRQ_check, which will loop
through all the pending interrupts for that VCPU. This is done while holding the
raw_lock, meaning that in all this time the interrupts and preemption are
disabled on the host Linux. A malicious user app can max both these number and
cause a DoS.

This temporary fix is sent for two reasons. First is so that users who want to
use the in-kernel MPIC emulation are aware of the potential latencies, thus
making sure that the hardware MPIC and their usage scenario does not involve
interrupts sent in directed delivery mode, and the number of possible pending
interrupts is kept small. Secondly, this should incentivize the development of a
proper openpic emulation that would be better suited for RT.

Acked-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Bogdan Purcareata <bogdan.purcareata@freescale.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

105/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: powerpc: Disable highmem on RT
Date: Mon, 18 Jul 2011 17:08:34 +0200

The current highmem handling on -RT is not compatible and needs fixups.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

106/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: mips: Disable highmem on RT
Date: Mon, 18 Jul 2011 17:10:12 +0200

The current highmem handling on -RT is not compatible and needs fixups.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

107/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: x86: Use generic rwsem_spinlocks on -rt
Date: Sun, 26 Jul 2009 02:21:32 +0200

Simplifies the separation of anon_rw_semaphores and rw_semaphores for
-rt.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

108/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: leds: trigger: disable CPU trigger on -RT
Date: Thu, 23 Jan 2014 14:45:59 +0100

as it triggers:
|CPU: 0 PID: 0 Comm: swapper Not tainted 3.12.8-rt10 #141
|[<c0014aa4>] (unwind_backtrace+0x0/0xf8) from [<c0012788>] (show_stack+0x1c/0x20)
|[<c0012788>] (show_stack+0x1c/0x20) from [<c043c8dc>] (dump_stack+0x20/0x2c)
|[<c043c8dc>] (dump_stack+0x20/0x2c) from [<c004c5e8>] (__might_sleep+0x13c/0x170)
|[<c004c5e8>] (__might_sleep+0x13c/0x170) from [<c043f270>] (__rt_spin_lock+0x28/0x38)
|[<c043f270>] (__rt_spin_lock+0x28/0x38) from [<c043fa00>] (rt_read_lock+0x68/0x7c)
|[<c043fa00>] (rt_read_lock+0x68/0x7c) from [<c036cf74>] (led_trigger_event+0x2c/0x5c)
|[<c036cf74>] (led_trigger_event+0x2c/0x5c) from [<c036e0bc>] (ledtrig_cpu+0x54/0x5c)
|[<c036e0bc>] (ledtrig_cpu+0x54/0x5c) from [<c000ffd8>] (arch_cpu_idle_exit+0x18/0x1c)
|[<c000ffd8>] (arch_cpu_idle_exit+0x18/0x1c) from [<c00590b8>] (cpu_startup_entry+0xa8/0x234)
|[<c00590b8>] (cpu_startup_entry+0xa8/0x234) from [<c043b2cc>] (rest_init+0xb8/0xe0)
|[<c043b2cc>] (rest_init+0xb8/0xe0) from [<c061ebe0>] (start_kernel+0x2c4/0x380)

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

109/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: cpufreq: drop K8's driver from beeing selected
Date: Thu, 9 Apr 2015 15:23:01 +0200

Ralf posted a picture of a backtrace from

| powernowk8_target_fn() -> transition_frequency_fidvid() and then at the
| end:
| 932         policy = cpufreq_cpu_get(smp_processor_id());
| 933         cpufreq_cpu_put(policy);

crashing the system on -RT. I assumed that policy was a NULL pointer but
was rulled out. Since Ralf can't do any more investigations on this and
I have no machine with this, I simply switch it off.

Reported-by: Ralf Mardorf <ralf.mardorf@alice-dsl.net>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

110/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: md: disable bcache
Date: Thu, 29 Aug 2013 11:48:57 +0200

It uses anon semaphores
|drivers/md/bcache/request.c: In function ‘cached_dev_write_complete’:
|drivers/md/bcache/request.c:1007:2: error: implicit declaration of function ‘up_read_non_owner’ [-Werror=implicit-function-declaration]
|  up_read_non_owner(&dc->writeback_lock);
|  ^
|drivers/md/bcache/request.c: In function ‘request_write’:
|drivers/md/bcache/request.c:1033:2: error: implicit declaration of function ‘down_read_non_owner’ [-Werror=implicit-function-declaration]
|  down_read_non_owner(&dc->writeback_lock);
|  ^

either we get rid of those or we have to introduce them…

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

111/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: efi: Disable runtime services on RT
Date: Thu, 26 Jul 2018 15:03:16 +0200

Based on meassurements the EFI functions get_variable /
get_next_variable take up to 2us which looks okay.
The functions get_time, set_time take around 10ms. Those 10ms are too
much. Even one ms would be too much.
Ard mentioned that SetVariable might even trigger larger latencies if
the firware will erase flash blocks on NOR.

The time-functions are used by efi-rtc and can be triggered during
runtimed (either via explicit read/write or ntp sync).

The variable write could be used by pstore.
These functions can be disabled without much of a loss. The poweroff /
reboot hooks may be provided by PSCI.

Disable EFI's runtime wrappers.

This was observed on "EFI v2.60 by SoftIron Overdrive 1000".

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

112/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: preempt: Provide preempt_*_(no)rt variants
Date: Fri, 24 Jul 2009 12:38:56 +0200

RT needs a few preempt_disable/enable points which are not necessary
otherwise. Implement variants to avoid #ifdeffery.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

113/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: futex: workaround migrate_disable/enable in different context
Date: Wed, 8 Mar 2017 14:23:35 +0100

migrate_disable()/migrate_enable() takes a different path in atomic() vs
!atomic() context. These little hacks ensure that we don't underflow / overflow
the migrate code counts properly while we lock the hb lockwith interrupts
enabled and unlock it with interrupts disabled.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

114/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rt: Add local irq locks
Date: Mon, 20 Jun 2011 09:03:47 +0200

Introduce locallock. For !RT this maps to preempt_disable()/
local_irq_disable() so there is not much that changes. For RT this will
map to a spinlock. This makes preemption possible and locked "ressource"
gets the lockdep anotation it wouldn't have otherwise. The locks are
recursive for owner == current. Also, all locks user migrate_disable()
which ensures that the task is not migrated to another CPU while the lock
is held and the owner is preempted.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

115/298 [
Author: Julia Cartwright
Email: julia@ni.com
Subject: locallock: provide {get,put}_locked_ptr() variants
Date: Mon, 7 May 2018 08:58:56 -0500

Provide a set of locallocked accessors for pointers to per-CPU data;
this is useful for dynamically-allocated per-CPU regions, for example.

These are symmetric with the {get,put}_cpu_ptr() per-CPU accessor
variants.

Signed-off-by: Julia Cartwright <julia@ni.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

116/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: mm/scatterlist: Do not disable irqs on RT
Date: Fri, 3 Jul 2009 08:44:34 -0500

For -RT it is enough to keep pagefault disabled (which is currently handled by
kmap_atomic()).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

117/298 [
Author: Oleg Nesterov
Email: oleg@redhat.com
Subject: signal/x86: Delay calling signals in atomic
Date: Tue, 14 Jul 2015 14:26:34 +0200

On x86_64 we must disable preemption before we enable interrupts
for stack faults, int3 and debugging, because the current task is using
a per CPU debug stack defined by the IST. If we schedule out, another task
can come in and use the same stack and cause the stack to be corrupted
and crash the kernel on return.

When CONFIG_PREEMPT_RT_FULL is enabled, spin_locks become mutexes, and
one of these is the spin lock used in signal handling.

Some of the debug code (int3) causes do_trap() to send a signal.
This function calls a spin lock that has been converted to a mutex
and has the possibility to sleep. If this happens, the above issues with
the corrupted stack is possible.

Instead of calling the signal right away, for PREEMPT_RT and x86_64,
the signal information is stored on the stacks task_struct and
TIF_NOTIFY_RESUME is set. Then on exit of the trap, the signal resume
code will send the signal when preemption is enabled.

[ rostedt: Switched from #ifdef CONFIG_PREEMPT_RT_FULL to
  ARCH_RT_DELAYS_SIGNAL_SEND and added comments to the code. ]

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

118/298 [
Author: Yang Shi
Email: yang.shi@linaro.org
Subject: x86/signal: delay calling signals on 32bit
Date: Thu, 10 Dec 2015 10:58:51 -0800

When running some ptrace single step tests on x86-32 machine, the below problem
is triggered:

BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:917
in_atomic(): 1, irqs_disabled(): 0, pid: 1041, name: dummy2
Preemption disabled at:[<c100326f>] do_debug+0x1f/0x1a0

CPU: 10 PID: 1041 Comm: dummy2 Tainted: G        W       4.1.13-rt13 #1
Call Trace:
 [<c1aa8306>] dump_stack+0x46/0x5c
 [<c1080517>] ___might_sleep+0x137/0x220
 [<c1ab0eff>] rt_spin_lock+0x1f/0x80
 [<c1064b5a>] do_force_sig_info+0x2a/0xc0
 [<c106567d>] force_sig_info+0xd/0x10
 [<c1010cff>] send_sigtrap+0x6f/0x80
 [<c10033b1>] do_debug+0x161/0x1a0
 [<c1ab2921>] debug_stack_correct+0x2e/0x35

This happens since 959274753857 ("x86, traps: Track entry into and exit
from IST context") which was merged in v4.1-rc1.

Signed-off-by: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

119/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: buffer_head: Replace bh_uptodate_lock for -rt
Date: Fri, 18 Mar 2011 09:18:52 +0100

Wrap the bit_spin_lock calls into a separate inline and add the RT
replacements with a real spinlock.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

120/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: fs: jbd/jbd2: Make state lock and journal head lock rt safe
Date: Fri, 18 Mar 2011 10:11:25 +0100

bit_spin_locks break under RT.

Based on a previous patch from Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
--
 include/linux/buffer_head.h |    8 ++++++++
 include/linux/jbd2.h        |   24 ++++++++++++++++++++++++
 2 files changed, 32 insertions(+)
]

121/298 [
Author: Paul Gortmaker
Email: paul.gortmaker@windriver.com
Subject: list_bl: Make list head locking RT safe
Date: Fri, 21 Jun 2013 15:07:25 -0400

As per changes in include/linux/jbd_common.h for avoiding the
bit_spin_locks on RT ("fs: jbd/jbd2: Make state lock and journal
head lock rt safe") we do the same thing here.

We use the non atomic __set_bit and __clear_bit inside the scope of
the lock to preserve the ability of the existing LIST_DEBUG code to
use the zero'th bit in the sanity checks.

As a bit spinlock, we had no lockdep visibility into the usage
of the list head locking.  Now, if we were to implement it as a
standard non-raw spinlock, we would see:

BUG: sleeping function called from invalid context at kernel/rtmutex.c:658
in_atomic(): 1, irqs_disabled(): 0, pid: 122, name: udevd
5 locks held by udevd/122:
 #0:  (&sb->s_type->i_mutex_key#7/1){+.+.+.}, at: [<ffffffff811967e8>] lock_rename+0xe8/0xf0
 #1:  (rename_lock){+.+...}, at: [<ffffffff811a277c>] d_move+0x2c/0x60
 #2:  (&dentry->d_lock){+.+...}, at: [<ffffffff811a0763>] dentry_lock_for_move+0xf3/0x130
 #3:  (&dentry->d_lock/2){+.+...}, at: [<ffffffff811a0734>] dentry_lock_for_move+0xc4/0x130
 #4:  (&dentry->d_lock/3){+.+...}, at: [<ffffffff811a0747>] dentry_lock_for_move+0xd7/0x130
Pid: 122, comm: udevd Not tainted 3.4.47-rt62 #7
Call Trace:
 [<ffffffff810b9624>] __might_sleep+0x134/0x1f0
 [<ffffffff817a24d4>] rt_spin_lock+0x24/0x60
 [<ffffffff811a0c4c>] __d_shrink+0x5c/0xa0
 [<ffffffff811a1b2d>] __d_drop+0x1d/0x40
 [<ffffffff811a24be>] __d_move+0x8e/0x320
 [<ffffffff811a278e>] d_move+0x3e/0x60
 [<ffffffff81199598>] vfs_rename+0x198/0x4c0
 [<ffffffff8119b093>] sys_renameat+0x213/0x240
 [<ffffffff817a2de5>] ? _raw_spin_unlock+0x35/0x60
 [<ffffffff8107781c>] ? do_page_fault+0x1ec/0x4b0
 [<ffffffff817a32ca>] ? retint_swapgs+0xe/0x13
 [<ffffffff813eb0e6>] ? trace_hardirqs_on_thunk+0x3a/0x3f
 [<ffffffff8119b0db>] sys_rename+0x1b/0x20
 [<ffffffff817a3b96>] system_call_fastpath+0x1a/0x1f

Since we are only taking the lock during short lived list operations,
lets assume for now that it being raw won't be a significant latency
concern.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

122/298 [
Author: Josh Cartwright
Email: joshc@ni.com
Subject: list_bl: fixup bogus lockdep warning
Date: Thu, 31 Mar 2016 00:04:25 -0500

At first glance, the use of 'static inline' seems appropriate for
INIT_HLIST_BL_HEAD().

However, when a 'static inline' function invocation is inlined by gcc,
all callers share any static local data declared within that inline
function.

This presents a problem for how lockdep classes are setup.  raw_spinlocks, for
example, when CONFIG_DEBUG_SPINLOCK,

	# define raw_spin_lock_init(lock)				\
	do {								\
		static struct lock_class_key __key;			\
									\
		__raw_spin_lock_init((lock), #lock, &__key);		\
	} while (0)

When this macro is expanded into a 'static inline' caller, like
INIT_HLIST_BL_HEAD():

	static inline INIT_HLIST_BL_HEAD(struct hlist_bl_head *h)
	{
		h->first = NULL;
		raw_spin_lock_init(&h->lock);
	}

...the static local lock_class_key object is made a function static.

For compilation units which initialize invoke INIT_HLIST_BL_HEAD() more
than once, then, all of the invocations share this same static local
object.

This can lead to some very confusing lockdep splats (example below).
Solve this problem by forcing the INIT_HLIST_BL_HEAD() to be a macro,
which prevents the lockdep class object sharing.

 =============================================
 [ INFO: possible recursive locking detected ]
 4.4.4-rt11 #4 Not tainted
 ---------------------------------------------
 kswapd0/59 is trying to acquire lock:
  (&h->lock#2){+.+.-.}, at: mb_cache_shrink_scan

 but task is already holding lock:
  (&h->lock#2){+.+.-.}, at:  mb_cache_shrink_scan

 other info that might help us debug this:
  Possible unsafe locking scenario:

        CPU0
        ----
   lock(&h->lock#2);
   lock(&h->lock#2);

  *** DEADLOCK ***

  May be due to missing lock nesting notation

 2 locks held by kswapd0/59:
  #0:  (shrinker_rwsem){+.+...}, at: rt_down_read_trylock
  #1:  (&h->lock#2){+.+.-.}, at: mb_cache_shrink_scan

Reported-by: Luis Claudio R. Goncalves <lclaudio@uudg.org>
Tested-by: Luis Claudio R. Goncalves <lclaudio@uudg.org>
Signed-off-by: Josh Cartwright <joshc@ni.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

123/298 [
Author: Ingo Molnar
Email: mingo@elte.hu
Subject: genirq: Disable irqpoll on -rt
Date: Fri, 3 Jul 2009 08:29:57 -0500

Creates long latencies for no value

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

124/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: genirq: Force interrupt thread on RT
Date: Sun, 3 Apr 2011 11:57:29 +0200

Force threaded_irqs and optimize the code (force_irqthreads) in regard
to this.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

125/298 [
Author: Peter Zijlstra
Email: peterz@infradead.org
Subject: Split IRQ-off and zone->lock while freeing pages from PCP list #2
Date: Mon, 28 May 2018 15:24:21 +0200

Split the IRQ-off section while accessing the PCP list from zone->lock
while freeing pages.
Introcude  isolate_pcp_pages() which separates the pages from the PCP
list onto a temporary list and then free the temporary list via
free_pcppages_bulk().

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

126/298 [
Author: Peter Zijlstra
Email: peterz@infradead.org
Subject: Split IRQ-off and zone->lock while freeing pages from PCP list #2
Date: Mon, 28 May 2018 15:24:21 +0200

Split the IRQ-off section while accessing the PCP list from zone->lock
while freeing pages.
Introcude  isolate_pcp_pages() which separates the pages from the PCP
list onto a temporary list and then free the temporary list via
free_pcppages_bulk().

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

127/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: mm/SLxB: change list_lock to raw_spinlock_t
Date: Mon, 28 May 2018 15:24:22 +0200

The list_lock is used with used with IRQs off on RT. Make it a raw_spinlock_t
otherwise the interrupts won't be disabled on -RT.  The locking rules remain
the same on !RT.
This patch changes it for SLAB and SLUB since both share the same header
file for struct kmem_cache_node defintion.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

128/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: mm/SLUB: delay giving back empty slubs to IRQ enabled regions
Date: Thu, 21 Jun 2018 17:29:19 +0200

__free_slab() is invoked with disabled interrupts which increases the
irq-off time while __free_pages() is doing the work.
Allow __free_slab() to be invoked with enabled interrupts and move
everything from interrupts-off invocations to a temporary per-CPU list
so it can be processed later.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

129/298 [
Author: Ingo Molnar
Email: mingo@elte.hu
Subject: mm: page_alloc: rt-friendly per-cpu pages
Date: Fri, 3 Jul 2009 08:29:37 -0500

rt-friendly per-cpu pages: convert the irqs-off per-cpu locking
method into a preemptible, explicit-per-cpu-locks method.

Contains fixes from:
	 Peter Zijlstra <a.p.zijlstra@chello.nl>
	 Thomas Gleixner <tglx@linutronix.de>

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

130/298 [
Author: Ingo Molnar
Email: mingo@elte.hu
Subject: mm/swap: Convert to percpu locked
Date: Fri, 3 Jul 2009 08:29:51 -0500

Replace global locks (get_cpu + local_irq_save) with "local_locks()".
Currently there is one of for "rotate" and one for "swap".

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

131/298 [
Author: Luiz Capitulino
Email: lcapitulino@redhat.com
Subject: mm: perform lru_add_drain_all() remotely
Date: Fri, 27 May 2016 15:03:28 +0200

lru_add_drain_all() works by scheduling lru_add_drain_cpu() to run
on all CPUs that have non-empty LRU pagevecs and then waiting for
the scheduled work to complete. However, workqueue threads may never
have the chance to run on a CPU that's running a SCHED_FIFO task.
This causes lru_add_drain_all() to block forever.

This commit solves this problem by changing lru_add_drain_all()
to drain the LRU pagevecs of remote CPUs. This is done by grabbing
swapvec_lock and calling lru_add_drain_cpu().

PS: This is based on an idea and initial implementation by
    Rik van Riel.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

132/298 [
Author: Ingo Molnar
Email: mingo@elte.hu
Subject: mm/vmstat: Protect per cpu variables with preempt disable on RT
Date: Fri, 3 Jul 2009 08:30:13 -0500

Disable preemption on -RT for the vmstat code. On vanila the code runs in
IRQ-off regions while on -RT it is not. "preempt_disable" ensures that the
same ressources is not updated in parallel due to preemption.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

133/298 [
Author: Frank Rowand
Email: frank.rowand@am.sony.com
Subject: ARM: Initialize split page table locks for vector page
Date: Sat, 1 Oct 2011 18:58:13 -0700

Without this patch, ARM can not use SPLIT_PTLOCK_CPUS if
PREEMPT_RT_FULL=y because vectors_user_mapping() creates a
VM_ALWAYSDUMP mapping of the vector page (address 0xffff0000), but no
ptl->lock has been allocated for the page.  An attempt to coredump
that page will result in a kernel NULL pointer dereference when
follow_page() attempts to lock the page.

The call tree to the NULL pointer dereference is:

   do_notify_resume()
      get_signal_to_deliver()
         do_coredump()
            elf_core_dump()
               get_dump_page()
                  __get_user_pages()
                     follow_page()
                        pte_offset_map_lock() <----- a #define
                           ...
                              rt_spin_lock()

The underlying problem is exposed by mm-shrink-the-page-frame-to-rt-size.patch.

Signed-off-by: Frank Rowand <frank.rowand@am.sony.com>
Cc: Frank <Frank_Rowand@sonyusa.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/4E87C535.2030907@am.sony.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

134/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: mm: Enable SLUB for RT
Date: Thu, 25 Oct 2012 10:32:35 +0100

Avoid the memory allocation in IRQ section

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[bigeasy: factor out everything except the kcalloc() workaorund ]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

135/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: slub: Enable irqs for __GFP_WAIT
Date: Wed, 9 Jan 2013 12:08:15 +0100

SYSTEM_RUNNING might be too late for enabling interrupts. Allocations
with GFP_WAIT can happen before that. So use this as an indicator.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

136/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: slub: Disable SLUB_CPU_PARTIAL
Date: Wed, 15 Apr 2015 19:00:47 +0200

|BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:915
|in_atomic(): 1, irqs_disabled(): 0, pid: 87, name: rcuop/7
|1 lock held by rcuop/7/87:
| #0:  (rcu_callback){......}, at: [<ffffffff8112c76a>] rcu_nocb_kthread+0x1ca/0x5d0
|Preemption disabled at:[<ffffffff811eebd9>] put_cpu_partial+0x29/0x220
|
|CPU: 0 PID: 87 Comm: rcuop/7 Tainted: G        W       4.0.0-rt0+ #477
|Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
| 000000000007a9fc ffff88013987baf8 ffffffff817441c7 0000000000000007
| 0000000000000000 ffff88013987bb18 ffffffff810eee51 0000000000000000
| ffff88013fc10200 ffff88013987bb48 ffffffff8174a1c4 000000000007a9fc
|Call Trace:
| [<ffffffff817441c7>] dump_stack+0x4f/0x90
| [<ffffffff810eee51>] ___might_sleep+0x121/0x1b0
| [<ffffffff8174a1c4>] rt_spin_lock+0x24/0x60
| [<ffffffff811a689a>] __free_pages_ok+0xaa/0x540
| [<ffffffff811a729d>] __free_pages+0x1d/0x30
| [<ffffffff811eddd5>] __free_slab+0xc5/0x1e0
| [<ffffffff811edf46>] free_delayed+0x56/0x70
| [<ffffffff811eecfd>] put_cpu_partial+0x14d/0x220
| [<ffffffff811efc98>] __slab_free+0x158/0x2c0
| [<ffffffff811f0021>] kmem_cache_free+0x221/0x2d0
| [<ffffffff81204d0c>] file_free_rcu+0x2c/0x40
| [<ffffffff8112c7e3>] rcu_nocb_kthread+0x243/0x5d0
| [<ffffffff810e951c>] kthread+0xfc/0x120
| [<ffffffff8174abc8>] ret_from_fork+0x58/0x90

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

137/298 [
Author: Yang Shi
Email: yang.shi@windriver.com
Subject: mm/memcontrol: Don't call schedule_work_on in preemption disabled context
Date: Wed, 30 Oct 2013 11:48:33 -0700

The following trace is triggered when running ltp oom test cases:

BUG: sleeping function called from invalid context at kernel/rtmutex.c:659
in_atomic(): 1, irqs_disabled(): 0, pid: 17188, name: oom03
Preemption disabled at:[<ffffffff8112ba70>] mem_cgroup_reclaim+0x90/0xe0

CPU: 2 PID: 17188 Comm: oom03 Not tainted 3.10.10-rt3 #2
Hardware name: Intel Corporation Calpella platform/MATXM-CORE-411-B, BIOS 4.6.3 08/18/2010
ffff88007684d730 ffff880070df9b58 ffffffff8169918d ffff880070df9b70
ffffffff8106db31 ffff88007688b4a0 ffff880070df9b88 ffffffff8169d9c0
ffff88007688b4a0 ffff880070df9bc8 ffffffff81059da1 0000000170df9bb0
Call Trace:
[<ffffffff8169918d>] dump_stack+0x19/0x1b
[<ffffffff8106db31>] __might_sleep+0xf1/0x170
[<ffffffff8169d9c0>] rt_spin_lock+0x20/0x50
[<ffffffff81059da1>] queue_work_on+0x61/0x100
[<ffffffff8112b361>] drain_all_stock+0xe1/0x1c0
[<ffffffff8112ba70>] mem_cgroup_reclaim+0x90/0xe0
[<ffffffff8112beda>] __mem_cgroup_try_charge+0x41a/0xc40
[<ffffffff810f1c91>] ? release_pages+0x1b1/0x1f0
[<ffffffff8106f200>] ? sched_exec+0x40/0xb0
[<ffffffff8112cc87>] mem_cgroup_charge_common+0x37/0x70
[<ffffffff8112e2c6>] mem_cgroup_newpage_charge+0x26/0x30
[<ffffffff8110af68>] handle_pte_fault+0x618/0x840
[<ffffffff8103ecf6>] ? unpin_current_cpu+0x16/0x70
[<ffffffff81070f94>] ? migrate_enable+0xd4/0x200
[<ffffffff8110cde5>] handle_mm_fault+0x145/0x1e0
[<ffffffff810301e1>] __do_page_fault+0x1a1/0x4c0
[<ffffffff8169c9eb>] ? preempt_schedule_irq+0x4b/0x70
[<ffffffff8169e3b7>] ? retint_kernel+0x37/0x40
[<ffffffff8103053e>] do_page_fault+0xe/0x10
[<ffffffff8169e4c2>] page_fault+0x22/0x30

So, to prevent schedule_work_on from being called in preempt disabled context,
replace the pair of get/put_cpu() to get/put_cpu_light().

Signed-off-by: Yang Shi <yang.shi@windriver.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

138/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: mm/memcontrol: Replace local_irq_disable with local locks
Date: Wed, 28 Jan 2015 17:14:16 +0100

There are a few local_irq_disable() which then take sleeping locks. This
patch converts them local locks.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

139/298 [
Author: Mike Galbraith
Email: umgwanakikbuti@gmail.com
Subject: mm/zsmalloc: copy with get_cpu_var() and locking
Date: Tue, 22 Mar 2016 11:16:09 +0100

get_cpu_var() disables preemption and triggers a might_sleep() splat later.
This is replaced with get_locked_var().
This bitspinlocks are replaced with a proper mutex which requires a slightly
larger struct to allocate.

Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
[bigeasy: replace the bitspin_lock() with a mutex, get_locked_var(). Mike then
fixed the size magic]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

140/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: radix-tree: use local locks
Date: Wed, 25 Jan 2017 16:34:27 +0100

The preload functionality uses per-CPU variables and preempt-disable to
ensure that it does not switch CPUs during its usage. This patch adds
local_locks() instead preempt_disable() for the same purpose and to
remain preemptible on -RT.

Cc: stable-rt@vger.kernel.org
Reported-and-debugged-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

141/298 [
Author: Ingo Molnar
Email: mingo@elte.hu
Subject: timers: Prepare for full preemption
Date: Fri, 3 Jul 2009 08:29:34 -0500

When softirqs can be preempted we need to make sure that cancelling
the timer from the active thread can not deadlock vs. a running timer
callback. Add a waitqueue to resolve that.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

142/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: x86: kvm Require const tsc for RT
Date: Sun, 6 Nov 2011 12:26:18 +0100

Non constant TSC is a nightmare on bare metal already, but with
virtualization it becomes a complete disaster because the workarounds
are horrible latency wise. That's also a preliminary for running RT in
a guest on top of a RT host.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

143/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: pci/switchtec: Don't use completion's wait queue
Date: Wed, 4 Oct 2017 10:24:23 +0200

The poll callback is using completion's wait_queue_head_t member and
puts it in poll_wait() so the poll() caller gets a wakeup after command
completed. This does not work on RT because we don't have a
wait_queue_head_t in our completion implementation. Nobody in tree does
like that in tree so this is the only driver that breaks.

Instead of using the completion here is waitqueue with a status flag as
suggested by Logan.

I don't have the HW so I have no idea if it works as expected, so please
test it.

Cc: Kurt Schwemmer <kurt.schwemmer@microsemi.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

144/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: wait.h: include atomic.h
Date: Mon, 28 Oct 2013 12:19:57 +0100

|  CC      init/main.o
|In file included from include/linux/mmzone.h:9:0,
|                 from include/linux/gfp.h:4,
|                 from include/linux/kmod.h:22,
|                 from include/linux/module.h:13,
|                 from init/main.c:15:
|include/linux/wait.h: In function ‘wait_on_atomic_t’:
|include/linux/wait.h:982:2: error: implicit declaration of function ‘atomic_read’ [-Werror=implicit-function-declaration]
|  if (atomic_read(val) == 0)
|  ^

This pops up on ARM. Non-RT gets its atomic.h include from spinlock.h

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

145/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: kthread: add a global worker thread.
Date: Tue, 12 Feb 2019 15:09:38 +0100

Add kthread_schedule_work() which uses a global kthread for all its
jobs.
Split the cgroup include to avoid recussive includes from interrupt.h.
Fixup everything that fails to build (and did not include all header).

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

146/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: completion: Use simple wait queues
Date: Fri, 11 Jan 2013 11:23:51 +0100

Completions have no long lasting callbacks and therefor do not need
the complex waitqueue variant. Use simple waitqueues which reduces the
contention on the waitqueue lock.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

147/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: fs/aio: simple simple work
Date: Mon, 16 Feb 2015 18:49:10 +0100

|BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:768
|in_atomic(): 1, irqs_disabled(): 0, pid: 26, name: rcuos/2
|2 locks held by rcuos/2/26:
| #0:  (rcu_callback){.+.+..}, at: [<ffffffff810b1a12>] rcu_nocb_kthread+0x1e2/0x380
| #1:  (rcu_read_lock_sched){.+.+..}, at: [<ffffffff812acd26>] percpu_ref_kill_rcu+0xa6/0x1c0
|Preemption disabled at:[<ffffffff810b1a93>] rcu_nocb_kthread+0x263/0x380
|Call Trace:
| [<ffffffff81582e9e>] dump_stack+0x4e/0x9c
| [<ffffffff81077aeb>] __might_sleep+0xfb/0x170
| [<ffffffff81589304>] rt_spin_lock+0x24/0x70
| [<ffffffff811c5790>] free_ioctx_users+0x30/0x130
| [<ffffffff812ace34>] percpu_ref_kill_rcu+0x1b4/0x1c0
| [<ffffffff810b1a93>] rcu_nocb_kthread+0x263/0x380
| [<ffffffff8106e046>] kthread+0xd6/0xf0
| [<ffffffff81591eec>] ret_from_fork+0x7c/0xb0

replace this preempt_disable() friendly swork.

Reported-By: Mike Galbraith <umgwanakikbuti@gmail.com>
Suggested-by: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

148/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: genirq: Do not invoke the affinity callback via a workqueue on RT
Date: Wed, 21 Aug 2013 17:48:46 +0200

Joe Korty reported, that __irq_set_affinity_locked() schedules a
workqueue while holding a rawlock which results in a might_sleep()
warning.
This patch uses swork_queue() instead.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

149/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: psi: replace delayed work with timer + work
Date: Tue, 12 Feb 2019 15:03:03 +0100

psi_task_change() is invoked with disabled interrupts and this does not
allow to use schedule_delayed_work().

Replace schedule_delayed_work() with a timer which schedules the work
immediately.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

150/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: time/hrtimer: avoid schedule_work() with interrupts disabled
Date: Wed, 15 Nov 2017 17:29:51 +0100

The NOHZ code tries to schedule a workqueue with interrupts disabled.
Since this does not work -RT I am switching it to swork instead.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

151/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: hrtimer: consolidate hrtimer_init() + hrtimer_init_sleeper() calls
Date: Tue, 3 Jul 2018 11:25:41 +0200

hrtimer_init_sleeper() calls require a prior initialisation of the
hrtimer object with hrtimer_init(). Lets make the initialisation of
the hrtimer object part of hrtimer_init_sleeper(). To remain
consistent consider init_on_stack as well.

Beside adapting the hrtimer_init_sleeper[_on_stack]() functions, call
sites need to be updated as well.

Link: http://lkml.kernel.org/r/20180703092541.2870-1-anna-maria@linutronix.de


Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
[anna-maria: Updating the commit message, add staging/android/vsoc.c]
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
]

152/298 [
Author: Ingo Molnar
Email: mingo@elte.hu
Subject: hrtimers: Prepare full preemption
Date: Fri, 3 Jul 2009 08:29:34 -0500

Make cancellation of a running callback in softirq context safe
against preemption.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

153/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: hrtimer: by timers by default into the softirq context
Date: Fri, 3 Jul 2009 08:44:31 -0500

We can't have hrtimers callbacks running in hardirq context on RT. Therefore
the timers are deferred to the softirq context by default.
There are few timers which expect to be run in hardirq context even on RT.
Those are:
- very short running where low latency is critical (kvm lapic)
- timers which take raw locks and need run in hard-irq context (perf, sched)
- wake up related timer (kernel side of clock_nanosleep() and so on)

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

154/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: sched/fair: Make the hrtimers non-hard again
Date: Tue, 8 Jan 2019 12:31:06 +0100

Since commit "sched/fair: Robustify CFS-bandwidth timer locking" both
hrtimer can run in softirq context because now interrupts are disabled
as part of the locking procedure.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

155/298 [
Author: Yang Shi
Email: yang.shi@windriver.com
Subject: hrtimer: Move schedule_work call to helper thread
Date: Mon, 16 Sep 2013 14:09:19 -0700

When run ltp leapsec_timer test, the following call trace is caught:

BUG: sleeping function called from invalid context at kernel/rtmutex.c:659
in_atomic(): 1, irqs_disabled(): 1, pid: 0, name: swapper/1
Preemption disabled at:[<ffffffff810857f3>] cpu_startup_entry+0x133/0x310

CPU: 1 PID: 0 Comm: swapper/1 Not tainted 3.10.10-rt3 #2
Hardware name: Intel Corporation Calpella platform/MATXM-CORE-411-B, BIOS 4.6.3 08/18/2010
ffffffff81c2f800 ffff880076843e40 ffffffff8169918d ffff880076843e58
ffffffff8106db31 ffff88007684b4a0 ffff880076843e70 ffffffff8169d9c0
ffff88007684b4a0 ffff880076843eb0 ffffffff81059da1 0000001876851200
Call Trace:
<IRQ>  [<ffffffff8169918d>] dump_stack+0x19/0x1b
[<ffffffff8106db31>] __might_sleep+0xf1/0x170
[<ffffffff8169d9c0>] rt_spin_lock+0x20/0x50
[<ffffffff81059da1>] queue_work_on+0x61/0x100
[<ffffffff81065aa1>] clock_was_set_delayed+0x21/0x30
[<ffffffff810883be>] do_timer+0x40e/0x660
[<ffffffff8108f487>] tick_do_update_jiffies64+0xf7/0x140
[<ffffffff8108fe42>] tick_check_idle+0x92/0xc0
[<ffffffff81044327>] irq_enter+0x57/0x70
[<ffffffff816a040e>] smp_apic_timer_interrupt+0x3e/0x9b
[<ffffffff8169f80a>] apic_timer_interrupt+0x6a/0x70
<EOI>  [<ffffffff8155ea1c>] ? cpuidle_enter_state+0x4c/0xc0
[<ffffffff8155eb68>] cpuidle_idle_call+0xd8/0x2d0
[<ffffffff8100b59e>] arch_cpu_idle+0xe/0x30
[<ffffffff8108585e>] cpu_startup_entry+0x19e/0x310
[<ffffffff8168efa2>] start_secondary+0x1ad/0x1b0

The clock_was_set_delayed is called in hard IRQ handler (timer interrupt), which
calls schedule_work.

Under PREEMPT_RT_FULL, schedule_work calls spinlocks which could sleep, so it's
not safe to call schedule_work in interrupt context.

Reference upstream commit b68d61c705ef02384c0538b8d9374545097899ca
(rt,ntp: Move call to schedule_delayed_work() to helper thread)
from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-stable-rt.git

, which
makes a similar change.

Signed-off-by: Yang Shi <yang.shi@windriver.com>
[bigeasy: use kthread_schedule_work() instead a helper thread]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

156/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: hrtimer: move state change before hrtimer_cancel in do_nanosleep()
Date: Thu, 6 Dec 2018 10:15:13 +0100

There is a small window between setting t->task to NULL and waking the
task up (which would set TASK_RUNNING). So the timer would fire, run and
set ->task to NULL while the other side/do_nanosleep() wouldn't enter
freezable_schedule(). After all we are peemptible here (in
do_nanosleep() and on the timer wake up path) and on KVM/virt the
virt-CPU might get preempted.
So do_nanosleep() wouldn't enter freezable_schedule() but cancel the
timer which is still running and wait for it via
hrtimer_wait_for_timer(). Then wait_event()/might_sleep() would complain
that it is invoked with state != TASK_RUNNING.
This isn't a problem since it would be reset to TASK_RUNNING later
anyway and we don't rely on the previous state.

Move the state update to TASK_RUNNING before hrtimer_cancel() so there
are no complains from might_sleep() about wrong state.

Cc: stable-rt@vger.kernel.org
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

157/298 [
Author: John Stultz
Email: johnstul@us.ibm.com
Subject: posix-timers: Thread posix-cpu-timers on -rt
Date: Fri, 3 Jul 2009 08:29:58 -0500

posix-cpu-timer code takes non -rt safe locks in hard irq
context. Move it to a thread.

[ 3.0 fixes from Peter Zijlstra <peterz@infradead.org> ]

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

158/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: sched: Move task_struct cleanup to RCU
Date: Tue, 31 May 2011 16:59:16 +0200

__put_task_struct() does quite some expensive work. We don't want to
burden random tasks with that.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

159/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: sched: Limit the number of task migrations per batch
Date: Mon, 6 Jun 2011 12:12:51 +0200

Put an upper limit on the number of tasks which are migrated per batch
to avoid large latencies.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

160/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: sched: Move mmdrop to RCU on RT
Date: Mon, 6 Jun 2011 12:20:33 +0200

Takes sleeping locks and calls into the memory allocator, so nothing
we want to do in task switch and oder atomic contexts.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

161/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: kernel/sched: move stack + kprobe clean up to __put_task_struct()
Date: Mon, 21 Nov 2016 19:31:08 +0100

There is no need to free the stack before the task struct (except for reasons
mentioned in commit 68f24b08ee89 ("sched/core: Free the stack early if
CONFIG_THREAD_INFO_IN_TASK")). This also comes handy on -RT because we can't
free memory in preempt disabled region.

Cc: stable-rt@vger.kernel.org #for kprobe_flush_task()
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

162/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: sched: Add saved_state for tasks blocked on sleeping locks
Date: Sat, 25 Jun 2011 09:21:04 +0200

Spinlocks are state preserving in !RT. RT changes the state when a
task gets blocked on a lock. So we need to remember the state before
the lock contention. If a regular wakeup (not a RTmutex related
wakeup) happens, the saved_state is updated to running. When the lock
sleep is done, the saved state is restored.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

163/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: sched: Do not account rcu_preempt_depth on RT in might_sleep()
Date: Tue, 7 Jun 2011 09:19:06 +0200

RT changes the rcu_preempt_depth semantics, so we cannot check for it
in might_sleep().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

164/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: sched: Use the proper LOCK_OFFSET for cond_resched()
Date: Sun, 17 Jul 2011 22:51:33 +0200

RT does not increment preempt count when a 'sleeping' spinlock is
locked. Update PREEMPT_LOCK_OFFSET for that case.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

165/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: sched: Disable TTWU_QUEUE on RT
Date: Tue, 13 Sep 2011 16:42:35 +0200

The queued remote wakeup mechanism can introduce rather large
latencies if the number of migrated tasks is high. Disable it for RT.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

166/298 [
Author: Steven Rostedt
Email: rostedt@goodmis.org
Subject: sched/workqueue: Only wake up idle workers if not blocked on sleeping spin lock
Date: Mon, 18 Mar 2013 15:12:49 -0400

In -rt, most spin_locks() turn into mutexes. One of these spin_lock
conversions is performed on the workqueue gcwq->lock. When the idle
worker is worken, the first thing it will do is grab that same lock and
it too will block, possibly jumping into the same code, but because
nr_running would already be decremented it prevents an infinite loop.

But this is still a waste of CPU cycles, and it doesn't follow the method
of mainline, as new workers should only be woken when a worker thread is
truly going to sleep, and not just blocked on a spin_lock().

Check the saved_state too before waking up new workers.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

167/298 [
Author: Daniel Bristot de Oliveira
Email: bristot@redhat.com
Subject: rt: Increase/decrease the nr of migratory tasks when enabling/disabling migration
Date: Mon, 26 Jun 2017 17:07:15 +0200

There is a problem in the migrate_disable()/enable() implementation
regarding the number of migratory tasks in the rt/dl RQs. The problem
is the following:

When a task is attached to the rt runqueue, it is checked if it either
can run in more than one CPU, or if it is with migration disable. If
either check is true, the rt_rq->rt_nr_migratory counter is not
increased. The counter increases otherwise.

When the task is detached, the same check is done. If either check is
true, the rt_rq->rt_nr_migratory counter is not decreased. The counter
decreases otherwise. The same check is done in the dl scheduler.

One important thing is that, migrate disable/enable does not touch this
counter for tasks attached to the rt rq. So suppose the following chain
of events.

Assumptions:
Task A is the only runnable task in A      Task B runs on the CPU B
Task A runs on CFS (non-rt)                Task B has RT priority
Thus, rt_nr_migratory is 0                 B is running
Task A can run on all CPUS.

Timeline:
        CPU A/TASK A                        CPU B/TASK B
A takes the rt mutex X                           .
A disables migration                             .
           .                          B tries to take the rt mutex X
           .                          As it is held by A {
           .                            A inherits the rt priority of B
           .                            A is dequeued from CFS RQ of CPU A
           .                            A is enqueued in the RT RQ of CPU A
           .                            As migration is disabled
           .                              rt_nr_migratory in A is not increased
           .
A enables migration
A releases the rt mutex X {
  A returns to its original priority
  A ask to be dequeued from RT RQ {
    As migration is now enabled and it can run on all CPUS {
       rt_nr_migratory should be decreased
       As rt_nr_migratory is 0, rt_nr_migratory under flows
    }
}

This variable is important because it notifies if there are more than one
runnable & migratory task in the runqueue. If there are more than one
tasks, the rt_rq is set as overloaded, and then tries to migrate some
tasks. This rule is important to keep the scheduler working conserving,
that is, in a system with M CPUs, the M highest priority tasks should be
running.

As rt_nr_migratory is unsigned, it will become > 0, notifying that the
RQ is overloaded, activating pushing mechanism without need.

This patch fixes this problem by decreasing/increasing the
rt/dl_nr_migratory in the migrate disable/enable operations.

Reported-by: Pei Zhang <pezhang@redhat.com>
Reported-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: linux-rt-users <linux-rt-users@vger.kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

168/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: hotplug: Lightweight get online cpus
Date: Wed, 15 Jun 2011 12:36:06 +0200

get_online_cpus() is a heavy weight function which involves a global
mutex. migrate_disable() wants a simpler construct which prevents only
a CPU from going doing while a task is in a migrate disabled section.

Implement a per cpu lockless mechanism, which serializes only in the
real unplug case on a global mutex. That serialization affects only
tasks on the cpu which should be brought down.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

169/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: trace: Add migrate-disabled counter to tracing output
Date: Sun, 17 Jul 2011 21:56:42 +0200

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

170/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: lockdep: Make it RT aware
Date: Sun, 17 Jul 2011 18:51:23 +0200

teach lockdep that we don't really do softirqs on -RT.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

171/298 [
Author: Ingo Molnar
Email: mingo@elte.hu
Subject: tasklet: Prevent tasklets from going into infinite spin in RT
Date: Tue, 29 Nov 2011 20:18:22 -0500

When CONFIG_PREEMPT_RT_FULL is enabled, tasklets run as threads,
and spinlocks turn are mutexes. But this can cause issues with
tasks disabling tasklets. A tasklet runs under ksoftirqd, and
if a tasklets are disabled with tasklet_disable(), the tasklet
count is increased. When a tasklet runs, it checks this counter
and if it is set, it adds itself back on the softirq queue and
returns.

The problem arises in RT because ksoftirq will see that a softirq
is ready to run (the tasklet softirq just re-armed itself), and will
not sleep, but instead run the softirqs again. The tasklet softirq
will still see that the count is non-zero and will not execute
the tasklet and requeue itself on the softirq again, which will
cause ksoftirqd to run it again and again and again.

It gets worse because ksoftirqd runs as a real-time thread.
If it preempted the task that disabled tasklets, and that task
has migration disabled, or can't run for other reasons, the tasklet
softirq will never run because the count will never be zero, and
ksoftirqd will go into an infinite loop. As an RT task, it this
becomes a big problem.

This is a hack solution to have tasklet_disable stop tasklets, and
when a tasklet runs, instead of requeueing the tasklet softirqd
it delays it. When tasklet_enable() is called, and tasklets are
waiting, then the tasklet_enable() will kick the tasklets to continue.
This prevents the lock up from ksoftirq going into an infinite loop.

[ rostedt@goodmis.org: ported to 3.0-rt ]

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

172/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: softirq: Check preemption after reenabling interrupts
Date: Sun, 13 Nov 2011 17:17:09 +0100

raise_softirq_irqoff() disables interrupts and wakes the softirq
daemon, but after reenabling interrupts there is no preemption check,
so the execution of the softirq thread might be delayed arbitrarily.

In principle we could add that check to local_irq_enable/restore, but
that's overkill as the rasie_softirq_irqoff() sections are the only
ones which show this behaviour.

Reported-by: Carsten Emde <cbe@osadl.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

173/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: softirq: Disable softirq stacks for RT
Date: Mon, 18 Jul 2011 13:59:17 +0200

Disable extra stacks for softirqs. We want to preempt softirqs and
having them on special IRQ-stack does not make this easier.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

174/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: softirq: Split softirq locks
Date: Thu, 4 Oct 2012 14:20:47 +0100

The 3.x RT series removed the split softirq implementation in favour
of pushing softirq processing into the context of the thread which
raised it. Though this prevents us from handling the various softirqs
at different priorities. Now instead of reintroducing the split
softirq threads we split the locks which serialize the softirq
processing.

If a softirq is raised in context of a thread, then the softirq is
noted on a per thread field, if the thread is in a bh disabled
region. If the softirq is raised from hard interrupt context, then the
bit is set in the flag field of ksoftirqd and ksoftirqd is invoked.
When a thread leaves a bh disabled region, then it tries to execute
the softirqs which have been raised in its own context. It acquires
the per softirq / per cpu lock for the softirq and then checks,
whether the softirq is still pending in the per cpu
local_softirq_pending() field. If yes, it runs the softirq. If no,
then some other task executed it already. This allows for zero config
softirq elevation in the context of user space tasks or interrupt
threads.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

175/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: net/core: use local_bh_disable() in netif_rx_ni()
Date: Fri, 16 Jun 2017 19:03:16 +0200

In 2004 netif_rx_ni() gained a preempt_disable() section around
netif_rx() and its do_softirq() + testing for it. The do_softirq() part
is required because netif_rx() raises the softirq but does not invoke
it. The preempt_disable() is required to remain on the same CPU which added the
skb to the per-CPU list.
All this can be avoided be putting this into a local_bh_disable()ed
section. The local_bh_enable() part will invoke do_softirq() if
required.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

176/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: genirq: Allow disabling of softirq processing in irq thread context
Date: Tue, 31 Jan 2012 13:01:27 +0100

The processing of softirqs in irq thread context is a performance gain
for the non-rt workloads of a system, but it's counterproductive for
interrupts which are explicitely related to the realtime
workload. Allow such interrupts to prevent softirq processing in their
thread context.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

177/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: softirq: split timer softirqs out of ksoftirqd
Date: Wed, 20 Jan 2016 16:34:17 +0100

The softirqd runs in -RT with SCHED_FIFO (prio 1) and deals mostly with
timer wakeup which can not happen in hardirq context. The prio has been
risen from the normal SCHED_OTHER so the timer wakeup does not happen
too late.
With enough networking load it is possible that the system never goes
idle and schedules ksoftirqd and everything else with a higher priority.
One of the tasks left behind is one of RCU's threads and so we see stalls
and eventually run out of memory.
This patch moves the TIMER and HRTIMER softirqs out of the `ksoftirqd`
thread into its own `ktimersoftd`. The former can now run SCHED_OTHER
(same as mainline) and the latter at SCHED_FIFO due to the wakeups.

From networking point of view: The NAPI callback runs after the network
interrupt thread completes. If its run time takes too long the NAPI code
itself schedules the `ksoftirqd`. Here in the thread it can run at
SCHED_OTHER priority and it won't defer RCU anymore.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

178/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: rtmutex: trylock is okay on -RT
Date: Wed, 2 Dec 2015 11:34:07 +0100

non-RT kernel could deadlock on rt_mutex_trylock() in softirq context. On
-RT we don't run softirqs in IRQ context but in thread context so it is
not a issue here.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

179/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: fs/nfs: turn rmdir_sem into a semaphore
Date: Thu, 15 Sep 2016 10:51:27 +0200

The RW semaphore had a reader side which used the _non_owner version
because it most likely took the reader lock in one thread and released it
in another which would cause lockdep to complain if the "regular"
version was used.
On -RT we need the owner because the rw lock is turned into a rtmutex.
The semaphores on the hand are "plain simple" and should work as
expected. We can't have multiple readers but on -RT we don't allow
multiple readers anyway so that is not a loss.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

180/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rtmutex: Handle the various new futex race conditions
Date: Fri, 10 Jun 2011 11:04:15 +0200

RT opens a few new interesting race conditions in the rtmutex/futex
combo due to futex hash bucket lock being a 'sleeping' spinlock and
therefor not disabling preemption.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

181/298 [
Author: Steven Rostedt
Email: rostedt@goodmis.org
Subject: futex: Fix bug on when a requeued RT task times out
Date: Tue, 14 Jul 2015 14:26:34 +0200

Requeue with timeout causes a bug with PREEMPT_RT_FULL.

The bug comes from a timed out condition.

	TASK 1				TASK 2
	------				------
    futex_wait_requeue_pi()
	futex_wait_queue_me()
	<timed out>

					double_lock_hb();

	raw_spin_lock(pi_lock);
	if (current->pi_blocked_on) {
	} else {
	    current->pi_blocked_on = PI_WAKE_INPROGRESS;
	    run_spin_unlock(pi_lock);
	    spin_lock(hb->lock); <-- blocked!

					plist_for_each_entry_safe(this) {
					    rt_mutex_start_proxy_lock();
						task_blocks_on_rt_mutex();
						BUG_ON(task->pi_blocked_on)!!!!

The BUG_ON() actually has a check for PI_WAKE_INPROGRESS, but the
problem is that, after TASK 1 sets PI_WAKE_INPROGRESS, it then tries to
grab the hb->lock, which it fails to do so. As the hb->lock is a mutex,
it will block and set the "pi_blocked_on" to the hb->lock.

When TASK 2 goes to requeue it, the check for PI_WAKE_INPROGESS fails
because the task1's pi_blocked_on is no longer set to that, but instead,
set to the hb->lock.

The fix:

When calling rt_mutex_start_proxy_lock() a check is made to see
if the proxy tasks pi_blocked_on is set. If so, exit out early.
Otherwise set it to a new flag PI_REQUEUE_INPROGRESS, which notifies
the proxy task that it is being requeued, and will handle things
appropriately.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

182/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: futex: Ensure lock/unlock symetry versus pi_lock and hash bucket lock
Date: Fri, 1 Mar 2013 11:17:42 +0100

In exit_pi_state_list() we have the following locking construct:

   spin_lock(&hb->lock);
   raw_spin_lock_irq(&curr->pi_lock);

   ...
   spin_unlock(&hb->lock);

In !RT this works, but on RT the migrate_enable() function which is
called from spin_unlock() sees atomic context due to the held pi_lock
and just decrements the migrate_disable_atomic counter of the
task. Now the next call to migrate_disable() sees the counter being
negative and issues a warning. That check should be in
migrate_enable() already.

Fix this by dropping pi_lock before unlocking hb->lock and reaquire
pi_lock after that again. This is safe as the loop code reevaluates
head again under the pi_lock.

Reported-by: Yong Zhang <yong.zhang@windriver.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

183/298 [
Author: Grygorii Strashko
Email: Grygorii.Strashko@linaro.org
Subject: pid.h: include atomic.h
Date: Tue, 21 Jul 2015 19:43:56 +0300

This patch fixes build error:
  CC      kernel/pid_namespace.o
In file included from kernel/pid_namespace.c:11:0:
include/linux/pid.h: In function 'get_pid':
include/linux/pid.h:78:3: error: implicit declaration of function 'atomic_inc' [-Werror=implicit-function-declaration]
   atomic_inc(&pid->count);
   ^
which happens when
 CONFIG_PROVE_LOCKING=n
 CONFIG_DEBUG_SPINLOCK=n
 CONFIG_DEBUG_MUTEXES=n
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_PID_NS=y

Vanilla gets this via spinlock.h.

Signed-off-by: Grygorii Strashko <Grygorii.Strashko@linaro.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

184/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: arm: include definition for cpumask_t
Date: Thu, 22 Dec 2016 17:28:33 +0100

This definition gets pulled in by other files. With the (later) split of
RCU and spinlock.h it won't compile anymore.
The split is done in ("rbtree: don't include the rcu header").

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

185/298 [
Author: Wolfgang M. Reimer
Email: linuxball@gmail.com
Subject: locking: locktorture: Do NOT include rwlock.h directly
Date: Tue, 21 Jul 2015 16:20:07 +0200

Including rwlock.h directly will cause kernel builds to fail
if CONFIG_PREEMPT_RT_FULL is defined. The correct header file
(rwlock_rt.h OR rwlock.h) will be included by spinlock.h which
is included by locktorture.c anyway.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Wolfgang M. Reimer <linuxball@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

186/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rtmutex: Add rtmutex_lock_killable()
Date: Thu, 9 Jun 2011 11:43:52 +0200

Add "killable" type to rtmutex. We need this since rtmutex are used as
"normal" mutexes which do use this type.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

187/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rtmutex: Make lock_killable work
Date: Sat, 1 Apr 2017 12:50:59 +0200

Locking an rt mutex killable does not work because signal handling is
restricted to TASK_INTERRUPTIBLE.

Use signal_pending_state() unconditionaly.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

188/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: spinlock: Split the lock types header
Date: Wed, 29 Jun 2011 19:34:01 +0200

Split raw_spinlock into its own file and the remaining spinlock_t into
its own non-RT header. The non-RT header will be replaced later by sleeping
spinlocks.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

189/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rtmutex: Avoid include hell
Date: Wed, 29 Jun 2011 20:06:39 +0200

Include only the required raw types. This avoids pulling in the
complete spinlock header which in turn requires rtmutex.h at some point.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

190/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: rbtree: don't include the rcu header
Date: Thu, 21 Mar 2019 11:41:15 -0400

The RCU header pulls in spinlock.h and fails due not yet defined types:

|In file included from include/linux/spinlock.h:275:0,
|                 from include/linux/rcupdate.h:38,
|                 from include/linux/rbtree.h:34,
|                 from include/linux/rtmutex.h:17,
|                 from include/linux/spinlock_types.h:18,
|                 from kernel/bounds.c:13:
|include/linux/rwlock_rt.h:16:38: error: unknown type name ‘rwlock_t’
| extern void __lockfunc rt_write_lock(rwlock_t *rwlock);
|                                      ^

This patch moves the required RCU function from the rcupdate.h header file into
a new header file which can be included by both users.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

191/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rtmutex: Provide rt_mutex_slowlock_locked()
Date: Thu, 12 Oct 2017 16:14:22 +0200

This is the inner-part of rt_mutex_slowlock(), required for rwsem-rt.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

192/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rtmutex: export lockdep-less version of rt_mutex's lock, trylock and unlock
Date: Thu, 12 Oct 2017 16:36:39 +0200

Required for lock implementation ontop of rtmutex.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

193/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rtmutex: add sleeping lock implementation
Date: Thu, 12 Oct 2017 17:11:19 +0200

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

194/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rtmutex: add mutex implementation based on rtmutex
Date: Thu, 12 Oct 2017 17:17:03 +0200

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

195/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rtmutex: add rwsem implementation based on rtmutex
Date: Thu, 12 Oct 2017 17:28:34 +0200

The RT specific R/W semaphore implementation restricts the number of readers
to one because a writer cannot block on multiple readers and inherit its
priority or budget.

The single reader restricting is painful in various ways:

 - Performance bottleneck for multi-threaded applications in the page fault
   path (mmap sem)

 - Progress blocker for drivers which are carefully crafted to avoid the
   potential reader/writer deadlock in mainline.

The analysis of the writer code pathes shows, that properly written RT tasks
should not take them. Syscalls like mmap(), file access which take mmap sem
write locked have unbound latencies which are completely unrelated to mmap
sem. Other R/W sem users like graphics drivers are not suitable for RT tasks
either.

So there is little risk to hurt RT tasks when the RT rwsem implementation is
changed in the following way:

 - Allow concurrent readers

 - Make writers block until the last reader left the critical section. This
   blocking is not subject to priority/budget inheritance.

 - Readers blocked on a writer inherit their priority/budget in the normal
   way.

There is a drawback with this scheme. R/W semaphores become writer unfair
though the applications which have triggered writer starvation (mostly on
mmap_sem) in the past are not really the typical workloads running on a RT
system. So while it's unlikely to hit writer starvation, it's possible. If
there are unexpected workloads on RT systems triggering it, we need to rethink
the approach.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

196/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rtmutex: add rwlock implementation based on rtmutex
Date: Thu, 12 Oct 2017 17:18:06 +0200

The implementation is bias-based, similar to the rwsem implementation.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

197/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rtmutex: wire up RT's locking
Date: Thu, 12 Oct 2017 17:31:14 +0200

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

198/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: rtmutex: add ww_mutex addon for mutex-rt
Date: Thu, 12 Oct 2017 17:34:38 +0200

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

199/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: kconfig: Add PREEMPT_RT_FULL
Date: Wed, 29 Jun 2011 14:58:57 +0200

Introduce the final symbol for PREEMPT_RT_FULL.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

200/298 [
Author: Mikulas Patocka
Email: mpatocka@redhat.com
Subject: locking/rt-mutex: fix deadlock in device mapper / block-IO
Date: Mon, 13 Nov 2017 12:56:53 -0500

When some block device driver creates a bio and submits it to another
block device driver, the bio is added to current->bio_list (in order to
avoid unbounded recursion).

However, this queuing of bios can cause deadlocks, in order to avoid them,
device mapper registers a function flush_current_bio_list. This function
is called when device mapper driver blocks. It redirects bios queued on
current->bio_list to helper workqueues, so that these bios can proceed
even if the driver is blocked.

The problem with CONFIG_PREEMPT_RT_FULL is that when the device mapper
driver blocks, it won't call flush_current_bio_list (because
tsk_is_pi_blocked returns true in sched_submit_work), so deadlocks in
block device stack can happen.

Note that we can't call blk_schedule_flush_plug if tsk_is_pi_blocked
returns true - that would cause
BUG_ON(rt_mutex_real_waiter(task->pi_blocked_on)) in
task_blocks_on_rt_mutex when flush_current_bio_list attempts to take a
spinlock.

So the proper fix is to call blk_schedule_flush_plug in rt_mutex_fastlock,
when fast acquire failed and when the task is about to block.

CC: stable-rt@vger.kernel.org
[bigeasy: The deadlock is not device-mapper specific, it can also occur
          in plain EXT4]
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

201/298 [
Author: Scott Wood
Email: swood@redhat.com
Subject: locking/rt-mutex: Flush block plug on __down_read()
Date: Fri, 4 Jan 2019 15:33:21 -0500

__down_read() bypasses the rtmutex frontend to call
rt_mutex_slowlock_locked() directly, and thus it needs to call
blk_schedule_flush_flug() itself.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Scott Wood <swood@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

202/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: locking/rtmutex: re-init the wait_lock in rt_mutex_init_proxy_locked()
Date: Thu, 16 Nov 2017 16:48:48 +0100

We could provide a key-class for the lockdep (and fixup all callers) or
move the init to all callers (like it was) in order to avoid lockdep
seeing a double-lock of the wait_lock.

Reported-by: Fernando Lopez-Lezcano <nando@ccrma.Stanford.EDU>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

203/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: ptrace: fix ptrace vs tasklist_lock race
Date: Thu, 29 Aug 2013 18:21:04 +0200

As explained by Alexander Fyodorov <halcy@yandex.ru>:

|read_lock(&tasklist_lock) in ptrace_stop() is converted to mutex on RT kernel,
|and it can remove __TASK_TRACED from task->state (by moving  it to
|task->saved_state). If parent does wait() on child followed by a sys_ptrace
|call, the following race can happen:
|
|- child sets __TASK_TRACED in ptrace_stop()
|- parent does wait() which eventually calls wait_task_stopped() and returns
|  child's pid
|- child blocks on read_lock(&tasklist_lock) in ptrace_stop() and moves
|  __TASK_TRACED flag to saved_state
|- parent calls sys_ptrace, which calls ptrace_check_attach() and wait_task_inactive()

The patch is based on his initial patch where an additional check is
added in case the __TASK_TRACED moved to ->saved_state. The pi_lock is
taken in case the caller is interrupted between looking into ->state and
->saved_state.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

204/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: rtmutex: annotate sleeping lock context
Date: Thu, 21 Sep 2017 14:25:13 +0200

The RCU code complains on schedule() within a rcu_readlock() section.
The valid scenario on -RT is if a sleeping is held. In order to suppress
the warning the mirgrate_disable counter was used to identify the
invocation of schedule() due to lock contention.

Grygorii Strashko report that during CPU hotplug we might see the
warning via
 rt_spin_lock() -> migrate_disable() -> pin_current_cpu() -> __read_rt_lock()

because the counter is not yet set.
It is also possible to trigger the warning from cpu_chill()
(seen on a kblockd_mod_delayed_work_on() caller).

To address this RCU warning I annotate the sleeping lock context. The
counter is incremented before migrate_disable() so the warning Grygorii
should not trigger anymore. Additionally I use that counter in
cpu_chill() to avoid the RCU warning from there.

Reported-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

205/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: sched/migrate_disable: fallback to preempt_disable() instead barrier()
Date: Thu, 5 Jul 2018 14:44:51 +0200

On SMP + !RT migrate_disable() is still around. It is not part of spin_lock()
anymore so it has almost no users. However the futex code has a workaround for
the !in_atomic() part of migrate disable which fails because the matching
migrade_disable() is no longer part of spin_lock().

On !SMP + !RT migrate_disable() is reduced to barrier(). This is not optimal
because we few spots where a "preempt_disable()" statement was replaced with
"migrate_disable()".

We also used the migration_disable counter to figure out if a sleeping lock is
acquired so RCU does not complain about schedule() during rcu_read_lock() while
a sleeping lock is held. This changed, we no longer use it, we have now a
sleeping_lock counter for the RCU purpose.

This means we can now:
- for SMP + RT_BASE
  full migration program, nothing changes here

- for !SMP + RT_BASE
  the migration counting is no longer required. It used to ensure that the task
  is not migrated to another CPU and that this CPU remains online. !SMP ensures
  that already.
  Move it to CONFIG_SCHED_DEBUG so the counting is done for debugging purpose
  only.

- for all other cases including !RT
  fallback to preempt_disable(). The only remaining users of migrate_disable()
  are those which were converted from preempt_disable() and the futex
  workaround which is already in the preempt_disable() section due to the
  spin_lock that is held.

Cc: stable-rt@vger.kernel.org
Reported-by:  <joe.korty@concurrent-rt.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

206/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: locking: don't check for __LINUX_SPINLOCK_TYPES_H on -RT archs
Date: Fri, 4 Aug 2017 17:40:42 +0200

Upstream uses arch_spinlock_t within spinlock_t and requests that
spinlock_types.h header file is included first.
On -RT we have the rt_mutex with its raw_lock wait_lock which needs
architectures' spinlock_types.h header file for its definition. However
we need rt_mutex first because it is used to build the spinlock_t so
that check does not work for us.
Therefore I am dropping that check.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

207/298 [
Author: Paul E. McKenney
Email: paulmck@linux.vnet.ibm.com
Subject: rcu: Eliminate softirq processing from rcutree
Date: Mon, 4 Nov 2013 13:21:10 -0800

Running RCU out of softirq is a problem for some workloads that would
like to manage RCU core processing independently of other softirq work,
for example, setting kthread priority.  This commit therefore moves the
RCU core work from softirq to a per-CPU/per-flavor SCHED_OTHER kthread
named rcuc.  The SCHED_OTHER approach avoids the scalability problems
that appeared with the earlier attempt to move RCU core processing to
from softirq to kthreads.  That said, kernels built with RCU_BOOST=y
will run the rcuc kthreads at the RCU-boosting priority.

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Mike Galbraith <bitbucket@online.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

208/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: srcu: Remove srcu_queue_delayed_work_on()
Date: Tue, 11 Dec 2018 12:12:38 +0100

srcu_queue_delayed_work_on() disables preemption (and therefore CPU
hotplug in RCU's case) and then checks based on its own accounting if a
CPU is online. If the CPU is online it uses queue_delayed_work_on()
otherwise it fallbacks to queue_delayed_work().
The problem here is that queue_work() on -RT does not work with disabled
preemption.

queue_work_on() works also on an offlined CPU. queue_delayed_work_on()
has the problem that it is possible to program a timer on an offlined
CPU. This timer will fire once the CPU is online again. But until then,
the timer remains programmed and nothing will happen.

Add a local timer which will fire (as requested per delay) on the local
CPU and then enqueue the work on the specific CPU.

RCUtorture testing with SRCU-P for 24h showed no problems.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
]

209/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: srcu: replace local_irqsave() with a locallock
Date: Thu, 12 Oct 2017 18:37:12 +0200

There are two instances which disable interrupts in order to become a
stable this_cpu_ptr() pointer. The restore part is coupled with
spin_unlock_irqrestore() which does not work on RT.
Replace the local_irq_save() call with the appropriate local_lock()
version of it.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

210/298 [
Author: Julia Cartwright
Email: julia@ni.com
Subject: rcu: enable rcu_normal_after_boot by default for RT
Date: Wed, 12 Oct 2016 11:21:14 -0500

The forcing of an expedited grace period is an expensive and very
RT-application unfriendly operation, as it forcibly preempts all running
tasks on CPUs which are preventing the gp from expiring.

By default, as a policy decision, disable the expediting of grace
periods (after boot) on configurations which enable PREEMPT_RT_FULL.

Suggested-by: Luiz Capitulino <lcapitulino@redhat.com>
Acked-by: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Julia Cartwright <julia@ni.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

211/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: tty/serial/omap: Make the locking RT aware
Date: Thu, 28 Jul 2011 13:32:57 +0200

The lock is a sleeping lock and local_irq_save() is not the
optimsation we are looking for. Redo it to make it work on -RT and
non-RT.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

212/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: tty/serial/pl011: Make the locking work on RT
Date: Tue, 8 Jan 2013 21:36:51 +0100

The lock is a sleeping lock and local_irq_save() is not the optimsation
we are looking for. Redo it to make it work on -RT and non-RT.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

213/298 [
Author: Kurt Kanzenbach
Email: kurt@linutronix.de
Subject: tty: serial: pl011: explicitly initialize the flags variable
Date: Mon, 24 Sep 2018 10:29:01 +0200

Silence the following gcc warning:

drivers/tty/serial/amba-pl011.c: In function ‘pl011_console_write’:
./include/linux/spinlock.h:260:3: warning: ‘flags’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   _raw_spin_unlock_irqrestore(lock, flags); \
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/tty/serial/amba-pl011.c:2214:16: note: ‘flags’ was declared here
  unsigned long flags;
                ^~~~~

The code is correct. Thus, initializing flags to zero doesn't change the
behavior and resolves the warning.

Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

214/298 [
Author: Ingo Molnar
Email: mingo@elte.hu
Subject: rt: Improve the serial console PASS_LIMIT
Date: Wed, 14 Dec 2011 13:05:54 +0100

Beyond the warning:

 drivers/tty/serial/8250/8250.c:1613:6: warning: unused variable ‘pass_counter’ [-Wunused-variable]

the solution of just looping infinitely was ugly - up it to 1 million to
give it a chance to continue in some really ugly situation.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

215/298 [
Author: Peter Zijlstra
Email: peterz@infradead.org
Subject: locking/percpu-rwsem: Remove preempt_disable variants
Date: Wed, 23 Nov 2016 16:29:32 +0100

Effective revert commit:

  87709e28dc7c ("fs/locks: Use percpu_down_read_preempt_disable()")

This is causing major pain for PREEMPT_RT and is only a very small
performance issue for PREEMPT=y.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
]

216/298 [
Author: Yong Zhang
Email: yong.zhang0@gmail.com
Subject: mm: Protect activate_mm() by preempt_[disable&enable]_rt()
Date: Tue, 15 May 2012 13:53:56 +0800

User preempt_*_rt instead of local_irq_*_rt or otherwise there will be
warning on ARM like below:

WARNING: at build/linux/kernel/smp.c:459 smp_call_function_many+0x98/0x264()
Modules linked in:
[<c0013bb4>] (unwind_backtrace+0x0/0xe4) from [<c001be94>] (warn_slowpath_common+0x4c/0x64)
[<c001be94>] (warn_slowpath_common+0x4c/0x64) from [<c001bec4>] (warn_slowpath_null+0x18/0x1c)
[<c001bec4>] (warn_slowpath_null+0x18/0x1c) from [<c0053ff8>](smp_call_function_many+0x98/0x264)
[<c0053ff8>] (smp_call_function_many+0x98/0x264) from [<c0054364>] (smp_call_function+0x44/0x6c)
[<c0054364>] (smp_call_function+0x44/0x6c) from [<c0017d50>] (__new_context+0xbc/0x124)
[<c0017d50>] (__new_context+0xbc/0x124) from [<c009e49c>] (flush_old_exec+0x460/0x5e4)
[<c009e49c>] (flush_old_exec+0x460/0x5e4) from [<c00d61ac>] (load_elf_binary+0x2e0/0x11ac)
[<c00d61ac>] (load_elf_binary+0x2e0/0x11ac) from [<c009d060>] (search_binary_handler+0x94/0x2a4)
[<c009d060>] (search_binary_handler+0x94/0x2a4) from [<c009e8fc>] (do_execve+0x254/0x364)
[<c009e8fc>] (do_execve+0x254/0x364) from [<c0010e84>] (sys_execve+0x34/0x54)
[<c0010e84>] (sys_execve+0x34/0x54) from [<c000da00>] (ret_fast_syscall+0x0/0x30)
---[ end trace 0000000000000002 ]---

The reason is that ARM need irq enabled when doing activate_mm().
According to mm-protect-activate-switch-mm.patch, actually
preempt_[disable|enable]_rt() is sufficient.

Inspired-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1337061236-1766-1-git-send-email-yong.zhang0@gmail.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

217/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: fs/dcache: bring back explicit INIT_HLIST_BL_HEAD init
Date: Wed, 13 Sep 2017 12:32:34 +0200

Commit 3d375d78593c ("mm: update callers to use HASH_ZERO flag") removed
INIT_HLIST_BL_HEAD and uses the ZERO flag instead for the init. However
on RT we have also a spinlock which needs an init call so we can't use
that.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

218/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: fs/dcache: disable preemption on i_dir_seq's write side
Date: Fri, 20 Oct 2017 11:29:53 +0200

i_dir_seq is an opencoded seqcounter. Based on the code it looks like we
could have two writers in parallel despite the fact that the d_lock is
held. The problem is that during the write process on RT the preemption
is still enabled and if this process is interrupted by a reader with RT
priority then we lock up.
To avoid that lock up I am disabling the preemption during the update.
The rename of i_dir_seq is here to ensure to catch new write sides in
future.

Cc: stable-rt@vger.kernel.org
Reported-by:  <Oleg.Karfich@wago.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

219/298 [
Author: Julia Cartwright
Email: julia@ni.com
Subject: squashfs: make use of local lock in multi_cpu decompressor
Date: Mon, 7 May 2018 08:58:57 -0500

Currently, the squashfs multi_cpu decompressor makes use of
get_cpu_ptr()/put_cpu_ptr(), which unconditionally disable preemption
during decompression.

Because the workload is distributed across CPUs, all CPUs can observe a
very high wakeup latency, which has been seen to be as much as 8000us.

Convert this decompressor to make use of a local lock, which will allow
execution of the decompressor with preemption-enabled, but also ensure
concurrent accesses to the percpu compressor data on the local CPU will
be serialized.

Cc: stable-rt@vger.kernel.org
Reported-by: Alexander Stein <alexander.stein@systec-electronic.com>
Tested-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Julia Cartwright <julia@ni.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

220/298 [
Author: Daniel Wagner
Email: wagi@monom.org
Subject: thermal: Defer thermal wakups to threads
Date: Tue, 17 Feb 2015 09:37:44 +0100

On RT the spin lock in pkg_temp_thermal_platfrom_thermal_notify will
call schedule while we run in irq context.

[<ffffffff816850ac>] dump_stack+0x4e/0x8f
[<ffffffff81680f7d>] __schedule_bug+0xa6/0xb4
[<ffffffff816896b4>] __schedule+0x5b4/0x700
[<ffffffff8168982a>] schedule+0x2a/0x90
[<ffffffff8168a8b5>] rt_spin_lock_slowlock+0xe5/0x2d0
[<ffffffff8168afd5>] rt_spin_lock+0x25/0x30
[<ffffffffa03a7b75>] pkg_temp_thermal_platform_thermal_notify+0x45/0x134 [x86_pkg_temp_thermal]
[<ffffffff8103d4db>] ? therm_throt_process+0x1b/0x160
[<ffffffff8103d831>] intel_thermal_interrupt+0x211/0x250
[<ffffffff8103d8c1>] smp_thermal_interrupt+0x21/0x40
[<ffffffff8169415d>] thermal_interrupt+0x6d/0x80

Let's defer the work to a kthread.

Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
[bigeasy: reoder init/denit position. TODO: flush swork on exit]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

221/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: fs/epoll: Do not disable preemption on RT
Date: Fri, 8 Jul 2011 16:35:35 +0200

ep_call_nested() takes a sleeping lock so we can't disable preemption.
The light version is enough since ep_call_nested() doesn't mind beeing
invoked twice on the same CPU.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

222/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: mm/vmalloc: Another preempt disable region which sucks
Date: Tue, 12 Jul 2011 11:39:36 +0200

Avoid the preempt disable version of get_cpu_var(). The inner-lock should
provide enough serialisation.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

223/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: block: mq: use cpu_light()
Date: Wed, 9 Apr 2014 10:37:23 +0200

there is a might sleep splat because get_cpu() disables preemption and
later we grab a lock. As a workaround for this we use get_cpu_light().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

224/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: block/mq: do not invoke preempt_disable()
Date: Tue, 14 Jul 2015 14:26:34 +0200

preempt_disable() and get_cpu() don't play well together with the sleeping
locks it tries to allocate later.
It seems to be enough to replace it with get_cpu_light() and migrate_disable().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

225/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: block/mq: don't complete requests via IPI
Date: Thu, 29 Jan 2015 15:10:08 +0100

The IPI runs in hardirq context and there are sleeping locks. Assume caches are
shared and complete them on the local CPU.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

226/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: md: raid5: Make raid5_percpu handling RT aware
Date: Tue, 6 Apr 2010 16:51:31 +0200

__raid_run_ops() disables preemption with get_cpu() around the access
to the raid5_percpu variables. That causes scheduling while atomic
spews on RT.

Serialize the access to the percpu data with a lock and keep the code
preemptible.

Reported-by: Udo van den Heuvel <udovdh@xs4all.nl>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Udo van den Heuvel <udovdh@xs4all.nl>
]

227/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: rt: Introduce cpu_chill()
Date: Wed, 7 Mar 2012 20:51:03 +0100

Retry loops on RT might loop forever when the modifying side was
preempted. Add cpu_chill() to replace cpu_relax(). cpu_chill()
defaults to cpu_relax() for non RT. On RT it puts the looping task to
sleep for a tick so the preempted task can make progress.

Steven Rostedt changed it to use a hrtimer instead of msleep():
|
|Ulrich Obergfell pointed out that cpu_chill() calls msleep() which is woken
|up by the ksoftirqd running the TIMER softirq. But as the cpu_chill() is
|called from softirq context, it may block the ksoftirqd() from running, in
|which case, it may never wake up the msleep() causing the deadlock.

+ bigeasy later changed to schedule_hrtimeout()
|If a task calls cpu_chill() and gets woken up by a regular or spurious
|wakeup and has a signal pending, then it exits the sleep loop in
|do_nanosleep() and sets up the restart block. If restart->nanosleep.type is
|not TI_NONE then this results in accessing a stale user pointer from a
|previously interrupted syscall and a copy to user based on the stale
|pointer or a BUG() when 'type' is not supported in nanosleep_copyout().

+ bigeasy: add PF_NOFREEZE:
| [....] Waiting for /dev to be fully populated...
| =====================================
| [ BUG: udevd/229 still has locks held! ]
| 3.12.11-rt17 #23 Not tainted
| -------------------------------------
| 1 lock held by udevd/229:
|  #0:  (&type->i_mutex_dir_key#2){+.+.+.}, at: lookup_slow+0x28/0x98
|
| stack backtrace:
| CPU: 0 PID: 229 Comm: udevd Not tainted 3.12.11-rt17 #23
| (unwind_backtrace+0x0/0xf8) from (show_stack+0x10/0x14)
| (show_stack+0x10/0x14) from (dump_stack+0x74/0xbc)
| (dump_stack+0x74/0xbc) from (do_nanosleep+0x120/0x160)
| (do_nanosleep+0x120/0x160) from (hrtimer_nanosleep+0x90/0x110)
| (hrtimer_nanosleep+0x90/0x110) from (cpu_chill+0x30/0x38)
| (cpu_chill+0x30/0x38) from (dentry_kill+0x158/0x1ec)
| (dentry_kill+0x158/0x1ec) from (dput+0x74/0x15c)
| (dput+0x74/0x15c) from (lookup_real+0x4c/0x50)
| (lookup_real+0x4c/0x50) from (__lookup_hash+0x34/0x44)
| (__lookup_hash+0x34/0x44) from (lookup_slow+0x38/0x98)
| (lookup_slow+0x38/0x98) from (path_lookupat+0x208/0x7fc)
| (path_lookupat+0x208/0x7fc) from (filename_lookup+0x20/0x60)
| (filename_lookup+0x20/0x60) from (user_path_at_empty+0x50/0x7c)
| (user_path_at_empty+0x50/0x7c) from (user_path_at+0x14/0x1c)
| (user_path_at+0x14/0x1c) from (vfs_fstatat+0x48/0x94)
| (vfs_fstatat+0x48/0x94) from (SyS_stat64+0x14/0x30)
| (SyS_stat64+0x14/0x30) from (ret_fast_syscall+0x0/0x48)

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

228/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: block: blk-mq: move blk_queue_usage_counter_release() into process context
Date: Tue, 13 Mar 2018 13:49:16 +0100

| BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:914
| in_atomic(): 1, irqs_disabled(): 0, pid: 255, name: kworker/u257:6
| 5 locks held by kworker/u257:6/255:
|  #0:  ("events_unbound"){.+.+.+}, at: [<ffffffff8108edf1>] process_one_work+0x171/0x5e0
|  #1:  ((&entry->work)){+.+.+.}, at: [<ffffffff8108edf1>] process_one_work+0x171/0x5e0
|  #2:  (&shost->scan_mutex){+.+.+.}, at: [<ffffffffa000faa3>] __scsi_add_device+0xa3/0x130 [scsi_mod]
|  #3:  (&set->tag_list_lock){+.+...}, at: [<ffffffff812f09fa>] blk_mq_init_queue+0x96a/0xa50
|  #4:  (rcu_read_lock_sched){......}, at: [<ffffffff8132887d>] percpu_ref_kill_and_confirm+0x1d/0x120
| Preemption disabled at:[<ffffffff812eff76>] blk_mq_freeze_queue_start+0x56/0x70
|
| CPU: 2 PID: 255 Comm: kworker/u257:6 Not tainted 3.18.7-rt0+ #1
| Workqueue: events_unbound async_run_entry_fn
|  0000000000000003 ffff8800bc29f998 ffffffff815b3a12 0000000000000000
|  0000000000000000 ffff8800bc29f9b8 ffffffff8109aa16 ffff8800bc29fa28
|  ffff8800bc5d1bc8 ffff8800bc29f9e8 ffffffff815b8dd4 ffff880000000000
| Call Trace:
|  [<ffffffff815b3a12>] dump_stack+0x4f/0x7c
|  [<ffffffff8109aa16>] __might_sleep+0x116/0x190
|  [<ffffffff815b8dd4>] rt_spin_lock+0x24/0x60
|  [<ffffffff810b6089>] __wake_up+0x29/0x60
|  [<ffffffff812ee06e>] blk_mq_usage_counter_release+0x1e/0x20
|  [<ffffffff81328966>] percpu_ref_kill_and_confirm+0x106/0x120
|  [<ffffffff812eff76>] blk_mq_freeze_queue_start+0x56/0x70
|  [<ffffffff812f0000>] blk_mq_update_tag_set_depth+0x40/0xd0
|  [<ffffffff812f0a1c>] blk_mq_init_queue+0x98c/0xa50
|  [<ffffffffa000dcf0>] scsi_mq_alloc_queue+0x20/0x60 [scsi_mod]
|  [<ffffffffa000ea35>] scsi_alloc_sdev+0x2f5/0x370 [scsi_mod]
|  [<ffffffffa000f494>] scsi_probe_and_add_lun+0x9e4/0xdd0 [scsi_mod]
|  [<ffffffffa000fb26>] __scsi_add_device+0x126/0x130 [scsi_mod]
|  [<ffffffffa013033f>] ata_scsi_scan_host+0xaf/0x200 [libata]
|  [<ffffffffa012b5b6>] async_port_probe+0x46/0x60 [libata]
|  [<ffffffff810978fb>] async_run_entry_fn+0x3b/0xf0
|  [<ffffffff8108ee81>] process_one_work+0x201/0x5e0

percpu_ref_kill_and_confirm() invokes blk_mq_usage_counter_release() in
a rcu-sched region. swait based wake queue can't be used due to
wake_up_all() usage and disabled interrupts in !RT configs (as reported
by Corey Minyard).
The wq_has_sleeper() check has been suggested by Peter Zijlstra.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

229/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: block: Use cpu_chill() for retry loops
Date: Thu, 20 Dec 2012 18:28:26 +0100

Retry loops on RT might loop forever when the modifying side was
preempted. Steven also observed a live lock when there was a
concurrent priority boosting going on.

Use cpu_chill() instead of cpu_relax() to let the system
make progress.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

230/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: fs: dcache: Use cpu_chill() in trylock loops
Date: Wed, 7 Mar 2012 21:00:34 +0100

Retry loops on RT might loop forever when the modifying side was
preempted. Use cpu_chill() instead of cpu_relax() to let the system
make progress.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

231/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: net: Use cpu_chill() instead of cpu_relax()
Date: Wed, 7 Mar 2012 21:10:04 +0100

Retry loops on RT might loop forever when the modifying side was
preempted. Use cpu_chill() instead of cpu_relax() to let the system
make progress.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

232/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: fs/dcache: use swait_queue instead of waitqueue
Date: Wed, 14 Sep 2016 14:35:49 +0200

__d_lookup_done() invokes wake_up_all() while holding a hlist_bl_lock()
which disables preemption. As a workaround convert it to swait.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

233/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: workqueue: Use normal rcu
Date: Wed, 24 Jul 2013 15:26:54 +0200

There is no need for sched_rcu. The undocumented reason why sched_rcu
is used is to avoid a few explicit rcu_read_lock()/unlock() pairs by
abusing the fact that sched_rcu reader side critical sections are also
protected by preempt or irq disabled regions.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

234/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: workqueue: Use local irq lock instead of irq disable regions
Date: Sun, 17 Jul 2011 21:42:26 +0200

Use a local_irq_lock as a replacement for irq off regions. We keep the
semantic of irq-off in regard to the pool->lock and remain preemptible.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

235/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: workqueue: Prevent workqueue versus ata-piix livelock
Date: Mon, 1 Jul 2013 11:02:42 +0200

An Intel i7 system regularly detected rcu_preempt stalls after the kernel
was upgraded from 3.6-rt to 3.8-rt. When the stall happened, disk I/O was no
longer possible, unless the system was restarted.

The kernel message was:
INFO: rcu_preempt self-detected stall on CPU { 6}
[..]
NMI backtrace for cpu 6
CPU 6
Pid: 119, comm: irq/19-ata_piix Not tainted 3.8.13-rt13 #11 Shuttle Inc. SX58/SX58
RIP: 0010:[<ffffffff8124ca60>]  [<ffffffff8124ca60>] ip_compute_csum+0x30/0x30
RSP: 0018:ffff880333303cb0  EFLAGS: 00000002
RAX: 0000000000000006 RBX: 00000000000003e9 RCX: 0000000000000034
RDX: 0000000000000000 RSI: ffffffff81aa16d0 RDI: 0000000000000001
RBP: ffff880333303ce8 R08: ffffffff81aa16d0 R09: ffffffff81c1b8cc
R10: 0000000000000000 R11: 0000000000000000 R12: 000000000005161f
R13: 0000000000000006 R14: ffffffff81aa16d0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff880333300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 0000003c1b2bb420 CR3: 0000000001a0f000 CR4: 00000000000007e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process irq/19-ata_piix (pid: 119, threadinfo ffff88032d88a000, task ffff88032df80000)
Stack:
ffffffff8124cb32 000000000005161e 00000000000003e9 0000000000001000
0000000000009022 ffffffff81aa16d0 0000000000000002 ffff880333303cf8
ffffffff8124caa9 ffff880333303d08 ffffffff8124cad2 ffff880333303d28
Call Trace:
<IRQ>
[<ffffffff8124cb32>] ? delay_tsc+0x33/0xe3
[<ffffffff8124caa9>] __delay+0xf/0x11
[<ffffffff8124cad2>] __const_udelay+0x27/0x29
[<ffffffff8102d1fa>] native_safe_apic_wait_icr_idle+0x39/0x45
[<ffffffff8102dc9b>] __default_send_IPI_dest_field.constprop.0+0x1e/0x58
[<ffffffff8102dd1e>] default_send_IPI_mask_sequence_phys+0x49/0x7d
[<ffffffff81030326>] physflat_send_IPI_all+0x17/0x19
[<ffffffff8102de53>] arch_trigger_all_cpu_backtrace+0x50/0x79
[<ffffffff810b21d0>] rcu_check_callbacks+0x1cb/0x568
[<ffffffff81048c9c>] ? raise_softirq+0x2e/0x35
[<ffffffff81086be0>] ? tick_sched_do_timer+0x38/0x38
[<ffffffff8104f653>] update_process_times+0x44/0x55
[<ffffffff81086866>] tick_sched_handle+0x4a/0x59
[<ffffffff81086c1c>] tick_sched_timer+0x3c/0x5b
[<ffffffff81062845>] __run_hrtimer+0x9b/0x158
[<ffffffff810631d8>] hrtimer_interrupt+0x172/0x2aa
[<ffffffff8102d498>] smp_apic_timer_interrupt+0x76/0x89
[<ffffffff814d881d>] apic_timer_interrupt+0x6d/0x80
<EOI>
[<ffffffff81057cd2>] ? __local_lock_irqsave+0x17/0x4a
[<ffffffff81059336>] try_to_grab_pending+0x42/0x17e
[<ffffffff8105a699>] mod_delayed_work_on+0x32/0x88
[<ffffffff8105a70b>] mod_delayed_work+0x1c/0x1e
[<ffffffff8122ae84>] blk_run_queue_async+0x37/0x39
[<ffffffff81230985>] flush_end_io+0xf1/0x107
[<ffffffff8122e0da>] blk_finish_request+0x21e/0x264
[<ffffffff8122e162>] blk_end_bidi_request+0x42/0x60
[<ffffffff8122e1ba>] blk_end_request+0x10/0x12
[<ffffffff8132de46>] scsi_io_completion+0x1bf/0x492
[<ffffffff81335cec>] ? sd_done+0x298/0x2ef
[<ffffffff81325a02>] scsi_finish_command+0xe9/0xf2
[<ffffffff8132dbcb>] scsi_softirq_done+0x106/0x10f
[<ffffffff812333d3>] blk_done_softirq+0x77/0x87
[<ffffffff8104826f>] do_current_softirqs+0x172/0x2e1
[<ffffffff810aa820>] ? irq_thread_fn+0x3a/0x3a
[<ffffffff81048466>] local_bh_enable+0x43/0x72
[<ffffffff810aa866>] irq_forced_thread_fn+0x46/0x52
[<ffffffff810ab089>] irq_thread+0x8c/0x17c
[<ffffffff810ab179>] ? irq_thread+0x17c/0x17c
[<ffffffff810aaffd>] ? wake_threads_waitq+0x44/0x44
[<ffffffff8105eb18>] kthread+0x8d/0x95
[<ffffffff8105ea8b>] ? __kthread_parkme+0x65/0x65
[<ffffffff814d7b7c>] ret_from_fork+0x7c/0xb0
[<ffffffff8105ea8b>] ? __kthread_parkme+0x65/0x65

The state of softirqd of this CPU at the time of the crash was:
ksoftirqd/6     R  running task        0    53      2 0x00000000
ffff88032fc39d18 0000000000000046 ffff88033330c4c0 ffff8803303f4710
ffff88032fc39fd8 ffff88032fc39fd8 0000000000000000 0000000000062500
ffff88032df88000 ffff8803303f4710 0000000000000000 ffff88032fc38000
Call Trace:
[<ffffffff8105a3ae>] ? __queue_work+0x27c/0x27c
[<ffffffff814d178c>] preempt_schedule+0x61/0x76
[<ffffffff8106cccf>] migrate_enable+0xe5/0x1df
[<ffffffff8105a3ae>] ? __queue_work+0x27c/0x27c
[<ffffffff8104ef52>] run_timer_softirq+0x161/0x1d6
[<ffffffff8104826f>] do_current_softirqs+0x172/0x2e1
[<ffffffff8104840b>] run_ksoftirqd+0x2d/0x45
[<ffffffff8106658a>] smpboot_thread_fn+0x2ea/0x308
[<ffffffff810662a0>] ? test_ti_thread_flag+0xc/0xc
[<ffffffff810662a0>] ? test_ti_thread_flag+0xc/0xc
[<ffffffff8105eb18>] kthread+0x8d/0x95
[<ffffffff8105ea8b>] ? __kthread_parkme+0x65/0x65
[<ffffffff814d7afc>] ret_from_fork+0x7c/0xb0
[<ffffffff8105ea8b>] ? __kthread_parkme+0x65/0x65

Apparently, the softirq demon and the ata_piix IRQ handler were waiting
for each other to finish ending up in a livelock. After the below patch
was applied, the system no longer crashes.

Reported-by: Carsten Emde <C.Emde@osadl.org>
Proposed-by: Thomas Gleixner <tglx@linutronix.de>
Tested by: Carsten Emde <C.Emde@osadl.org>
Signed-off-by: Carsten Emde <C.Emde@osadl.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

236/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: sched: Distangle worker accounting from rqlock
Date: Wed, 22 Jun 2011 19:47:03 +0200

The worker accounting for cpu bound workers is plugged into the core
scheduler code and the wakeup code. This is not a hard requirement and
can be avoided by keeping track of the state in the workqueue code
itself.

Keep track of the sleeping state in the worker itself and call the
notifier before entering the core scheduler. There might be false
positives when the task is woken between that call and actually
scheduling, but that's not really different from scheduling and being
woken immediately after switching away. There is also no harm from
updating nr_running when the task returns from scheduling instead of
accounting it in the wakeup code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20110622174919.135236139@linutronix.de


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[bigeasy: preempt_disable() around wq_worker_sleeping() by Daniel Bristot de
          Oliveira]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

237/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: debugobjects: Make RT aware
Date: Sun, 17 Jul 2011 21:41:35 +0200

Avoid filling the pool / allocating memory with irqs off().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

238/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: seqlock: Prevent rt starvation
Date: Wed, 22 Feb 2012 12:03:30 +0100

If a low prio writer gets preempted while holding the seqlock write
locked, a high prio reader spins forever on RT.

To prevent this let the reader grab the spinlock, so it blocks and
eventually boosts the writer. This way the writer can proceed and
endless spinning is prevented.

For seqcount writers we disable preemption over the update code
path. Thanks to Al Viro for distangling some VFS code to make that
possible.

Nicholas Mc Guire:
- spin_lock+unlock => spin_unlock_wait
- __write_seqcount_begin => __raw_write_seqcount_begin

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

239/298 [
Author: Mike Galbraith
Email: umgwanakikbuti@gmail.com
Subject: sunrpc: Make svc_xprt_do_enqueue() use get_cpu_light()
Date: Wed, 18 Feb 2015 16:05:28 +0100

|BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:915
|in_atomic(): 1, irqs_disabled(): 0, pid: 3194, name: rpc.nfsd
|Preemption disabled at:[<ffffffffa06bf0bb>] svc_xprt_received+0x4b/0xc0 [sunrpc]
|CPU: 6 PID: 3194 Comm: rpc.nfsd Not tainted 3.18.7-rt1 #9
|Hardware name: MEDION MS-7848/MS-7848, BIOS M7848W08.404 11/06/2014
| ffff880409630000 ffff8800d9a33c78 ffffffff815bdeb5 0000000000000002
| 0000000000000000 ffff8800d9a33c98 ffffffff81073c86 ffff880408dd6008
| ffff880408dd6000 ffff8800d9a33cb8 ffffffff815c3d84 ffff88040b3ac000
|Call Trace:
| [<ffffffff815bdeb5>] dump_stack+0x4f/0x9e
| [<ffffffff81073c86>] __might_sleep+0xe6/0x150
| [<ffffffff815c3d84>] rt_spin_lock+0x24/0x50
| [<ffffffffa06beec0>] svc_xprt_do_enqueue+0x80/0x230 [sunrpc]
| [<ffffffffa06bf0bb>] svc_xprt_received+0x4b/0xc0 [sunrpc]
| [<ffffffffa06c03ed>] svc_add_new_perm_xprt+0x6d/0x80 [sunrpc]
| [<ffffffffa06b2693>] svc_addsock+0x143/0x200 [sunrpc]
| [<ffffffffa072e69c>] write_ports+0x28c/0x340 [nfsd]
| [<ffffffffa072d2ac>] nfsctl_transaction_write+0x4c/0x80 [nfsd]
| [<ffffffff8117ee83>] vfs_write+0xb3/0x1d0
| [<ffffffff8117f889>] SyS_write+0x49/0xb0
| [<ffffffff815c4556>] system_call_fastpath+0x16/0x1b

Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

240/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: net: Use skbufhead with raw lock
Date: Tue, 12 Jul 2011 15:38:34 +0200

Use the rps lock as rawlock so we can keep irq-off regions. It looks low
latency. However we can't kfree() from this context therefore we defer this
to the softirq and use the tofree_queue list for it (similar to process_queue).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

241/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: net: move xmit_recursion to per-task variable on -RT
Date: Wed, 13 Jan 2016 15:55:02 +0100

A softirq on -RT can be preempted. That means one task is in
__dev_queue_xmit(), gets preempted and another task may enter
__dev_queue_xmit() aw well. netperf together with a bridge device
will then trigger the `recursion alert` because each task increments
the xmit_recursion variable which is per-CPU.
A virtual device like br0 is required to trigger this warning.

This patch moves the lock owner and counter to be per task instead per-CPU so
it counts the recursion properly on -RT. The owner is also a task now and not a
CPU number.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

242/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: net: provide a way to delegate processing a softirq to ksoftirqd
Date: Wed, 20 Jan 2016 15:39:05 +0100

If the NET_RX uses up all of his budget it moves the following NAPI
invocations into the `ksoftirqd`. On -RT it does not do so. Instead it
rises the NET_RX softirq in its current context again.

In order to get closer to mainline's behaviour this patch provides
__raise_softirq_irqoff_ksoft() which raises the softirq in the ksoftird.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

243/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: net: dev: always take qdisc's busylock in __dev_xmit_skb()
Date: Wed, 30 Mar 2016 13:36:29 +0200

The root-lock is dropped before dev_hard_start_xmit() is invoked and after
setting the __QDISC___STATE_RUNNING bit. If this task is now pushed away
by a task with a higher priority then the task with the higher priority
won't be able to submit packets to the NIC directly instead they will be
enqueued into the Qdisc. The NIC will remain idle until the task(s) with
higher priority leave the CPU and the task with lower priority gets back
and finishes the job.

If we take always the busylock we ensure that the RT task can boost the
low-prio task and submit the packet.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

244/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: net/Qdisc: use a seqlock instead seqcount
Date: Wed, 14 Sep 2016 17:36:35 +0200

The seqcount disables preemption on -RT while it is held which can't
remove. Also we don't want the reader to spin for ages if the writer is
scheduled out. The seqlock on the other hand will serialize / sleep on
the lock while writer is active.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

245/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: net: add back the missing serialization in ip_send_unicast_reply()
Date: Wed, 31 Aug 2016 17:21:56 +0200

Some time ago Sami Pietikäinen reported a crash on -RT in
ip_send_unicast_reply() which was later fixed by Nicholas Mc Guire
(v3.12.8-rt11). Later (v3.18.8) the code was reworked and I dropped the
patch. As it turns out it was mistake.
I have reports that the same crash is possible with a similar backtrace.
It seems that vanilla protects access to this_cpu_ptr() via
local_bh_disable(). This does not work the on -RT since we can have
NET_RX and NET_TX running in parallel on the same CPU.
This is brings back the old locks.

|Unable to handle kernel NULL pointer dereference at virtual address 00000010
|PC is at __ip_make_skb+0x198/0x3e8
|[<c04e39d8>] (__ip_make_skb) from [<c04e3ca8>] (ip_push_pending_frames+0x20/0x40)
|[<c04e3ca8>] (ip_push_pending_frames) from [<c04e3ff0>] (ip_send_unicast_reply+0x210/0x22c)
|[<c04e3ff0>] (ip_send_unicast_reply) from [<c04fbb54>] (tcp_v4_send_reset+0x190/0x1c0)
|[<c04fbb54>] (tcp_v4_send_reset) from [<c04fcc1c>] (tcp_v4_do_rcv+0x22c/0x288)
|[<c04fcc1c>] (tcp_v4_do_rcv) from [<c0474364>] (release_sock+0xb4/0x150)
|[<c0474364>] (release_sock) from [<c04ed904>] (tcp_close+0x240/0x454)
|[<c04ed904>] (tcp_close) from [<c0511408>] (inet_release+0x74/0x7c)
|[<c0511408>] (inet_release) from [<c0470728>] (sock_release+0x30/0xb0)
|[<c0470728>] (sock_release) from [<c0470abc>] (sock_close+0x1c/0x24)
|[<c0470abc>] (sock_close) from [<c0115ec4>] (__fput+0xe8/0x20c)
|[<c0115ec4>] (__fput) from [<c0116050>] (____fput+0x18/0x1c)
|[<c0116050>] (____fput) from [<c0058138>] (task_work_run+0xa4/0xb8)
|[<c0058138>] (task_work_run) from [<c0011478>] (do_work_pending+0xd0/0xe4)
|[<c0011478>] (do_work_pending) from [<c000e740>] (work_pending+0xc/0x20)
|Code: e3530001 8a000001 e3a00040 ea000011 (e5973010)

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

246/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: net: add a lock around icmp_sk()
Date: Wed, 31 Aug 2016 17:54:09 +0200

It looks like the this_cpu_ptr() access in icmp_sk() is protected with
local_bh_disable(). To avoid missing serialization in -RT I am adding
here a local lock. No crash has been observed, this is just precaution.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

247/298 [
Author: Steven Rostedt
Email: rostedt@goodmis.org
Subject: net: Have __napi_schedule_irqoff() disable interrupts on RT
Date: Tue, 6 Dec 2016 17:50:30 -0500

A customer hit a crash where the napi sd->poll_list became corrupted.
The customer had the bnx2x driver, which does a
__napi_schedule_irqoff() in its interrupt handler. Unfortunately, when
running with CONFIG_PREEMPT_RT_FULL, this interrupt handler is run as a
thread and is preemptable. The call to ____napi_schedule() must be done
with interrupts disabled to protect the per cpu softnet_data's
"poll_list, which is protected by disabling interrupts (disabling
preemption is enough when all interrupts are threaded and
local_bh_disable() can't preempt)."

As bnx2x isn't the only driver that does this, the safest thing to do
is to make __napi_schedule_irqoff() call __napi_schedule() instead when
CONFIG_PREEMPT_RT_FULL is enabled, which will call local_irq_save()
before calling ____napi_schedule().

Cc: stable-rt@vger.kernel.org
Signed-off-by: Steven Rostedt (Red Hat) <rostedt@goodmis.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

248/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: irqwork: push most work into softirq context
Date: Tue, 23 Jun 2015 15:32:51 +0200

Initially we defered all irqwork into softirq because we didn't want the
latency spikes if perf or another user was busy and delayed the RT task.
The NOHZ trigger (nohz_full_kick_work) was the first user that did not work
as expected if it did not run in the original irqwork context so we had to
bring it back somehow for it. push_irq_work_func is the second one that
requires this.

This patch adds the IRQ_WORK_HARD_IRQ which makes sure the callback runs
in raw-irq context. Everything else is defered into softirq context. Without
-RT we have the orignal behavior.

This patch incorporates tglx orignal work which revoked a little bringing back
the arch_irq_work_raise() if possible and a few fixes from Steven Rostedt and
Mike Galbraith,

[bigeasy: melt tglx's irq_work_tick_soft() which splits irq_work_tick() into a
          hard and soft variant]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

249/298 [
Author: Yadi.hu
Email: yadi.hu@windriver.com
Subject: ARM: enable irq in translation/section permission fault handlers
Date: Wed, 10 Dec 2014 10:32:09 +0800

Probably happens on all ARM, with
CONFIG_PREEMPT_RT_FULL
CONFIG_DEBUG_ATOMIC_SLEEP

This simple program....

int main() {
   *((char*)0xc0001000) = 0;
};

[ 512.742724] BUG: sleeping function called from invalid context at kernel/rtmutex.c:658
[ 512.743000] in_atomic(): 0, irqs_disabled(): 128, pid: 994, name: a
[ 512.743217] INFO: lockdep is turned off.
[ 512.743360] irq event stamp: 0
[ 512.743482] hardirqs last enabled at (0): [< (null)>] (null)
[ 512.743714] hardirqs last disabled at (0): [<c0426370>] copy_process+0x3b0/0x11c0
[ 512.744013] softirqs last enabled at (0): [<c0426370>] copy_process+0x3b0/0x11c0
[ 512.744303] softirqs last disabled at (0): [< (null)>] (null)
[ 512.744631] [<c041872c>] (unwind_backtrace+0x0/0x104)
[ 512.745001] [<c09af0c4>] (dump_stack+0x20/0x24)
[ 512.745355] [<c0462490>] (__might_sleep+0x1dc/0x1e0)
[ 512.745717] [<c09b6770>] (rt_spin_lock+0x34/0x6c)
[ 512.746073] [<c0441bf0>] (do_force_sig_info+0x34/0xf0)
[ 512.746457] [<c0442668>] (force_sig_info+0x18/0x1c)
[ 512.746829] [<c041d880>] (__do_user_fault+0x9c/0xd8)
[ 512.747185] [<c041d938>] (do_bad_area+0x7c/0x94)
[ 512.747536] [<c041d990>] (do_sect_fault+0x40/0x48)
[ 512.747898] [<c040841c>] (do_DataAbort+0x40/0xa0)
[ 512.748181] Exception stack(0xecaa1fb0 to 0xecaa1ff8)

Oxc0000000 belongs to kernel address space, user task can not be
allowed to access it. For above condition, correct result is that
test case should receive a “segment fault” and exits but not stacks.

the root cause is commit 02fe2845d6a8 ("avoid enabling interrupts in
prefetch/data abort handlers"),it deletes irq enable block in Data
abort assemble code and move them into page/breakpiont/alignment fault
handlers instead. But author does not enable irq in translation/section
permission fault handlers. ARM disables irq when it enters exception/
interrupt mode, if kernel doesn't enable irq, it would be still disabled
during translation/section permission fault.

We see the above splat because do_force_sig_info is still called with
IRQs off, and that code eventually does a:

        spin_lock_irqsave(&t->sighand->siglock, flags);

As this is architecture independent code, and we've not seen any other
need for other arch to have the siglock converted to raw lock, we can
conclude that we should enable irq for ARM translation/section
permission exception.

Signed-off-by: Yadi.hu <yadi.hu@windriver.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

250/298 [
Author: Josh Cartwright
Email: joshc@ni.com
Subject: genirq: update irq_set_irqchip_state documentation
Date: Thu, 11 Feb 2016 11:54:00 -0600

On -rt kernels, the use of migrate_disable()/migrate_enable() is
sufficient to guarantee a task isn't moved to another CPU.  Update the
irq_set_irqchip_state() documentation to reflect this.

Signed-off-by: Josh Cartwright <joshc@ni.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

251/298 [
Author: Josh Cartwright
Email: joshc@ni.com
Subject: KVM: arm/arm64: downgrade preempt_disable()d region to migrate_disable()
Date: Thu, 11 Feb 2016 11:54:01 -0600

kvm_arch_vcpu_ioctl_run() disables the use of preemption when updating
the vgic and timer states to prevent the calling task from migrating to
another CPU.  It does so to prevent the task from writing to the
incorrect per-CPU GIC distributor registers.

On -rt kernels, it's possible to maintain the same guarantee with the
use of migrate_{disable,enable}(), with the added benefit that the
migrate-disabled region is preemptible.  Update
kvm_arch_vcpu_ioctl_run() to do so.

Cc: Christoffer Dall <christoffer.dall@linaro.org>
Reported-by: Manish Jaggi <Manish.Jaggi@caviumnetworks.com>
Signed-off-by: Josh Cartwright <joshc@ni.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

252/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: arm64: fpsimd: use preemp_disable in addition to local_bh_disable()
Date: Wed, 25 Jul 2018 14:02:38 +0200

In v4.16-RT I noticed a number of warnings from task_fpsimd_load(). The
code disables BH and expects that it is not preemptible. On -RT the
task remains preemptible but remains the same CPU. This may corrupt the
content of the SIMD registers if the task is preempted during
saving/restoring those registers.

Add preempt_disable()/enable() to enfore the required semantic on -RT.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

253/298 [
Author: Clark Williams
Email: williams@redhat.com
Subject: sysfs: Add /sys/kernel/realtime entry
Date: Sat, 30 Jul 2011 21:55:53 -0500

Add a /sys/kernel entry to indicate that the kernel is a
realtime kernel.

Clark says that he needs this for udev rules, udev needs to evaluate
if its a PREEMPT_RT kernel a few thousand times and parsing uname
output is too slow or so.

Are there better solutions? Should it exist and return 0 on !-rt?

Signed-off-by: Clark Williams <williams@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
]

254/298 [
Author: Peter Zijlstra
Email: peterz@infradead.org
Subject: mm, rt: kmap_atomic scheduling
Date: Thu, 28 Jul 2011 10:43:51 +0200

In fact, with migrate_disable() existing one could play games with
kmap_atomic. You could save/restore the kmap_atomic slots on context
switch (if there are any in use of course), this should be esp easy now
that we have a kmap_atomic stack.

Something like the below.. it wants replacing all the preempt_disable()
stuff with pagefault_disable() && migrate_disable() of course, but then
you can flip kmaps around like below.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
[dvhart@linux.intel.com: build fix]
Link: http://lkml.kernel.org/r/1311842631.5890.208.camel@twins



[tglx@linutronix.de: Get rid of the per cpu variable and store the idx
		     and the pte content right away in the task struct.
		     Shortens the context switch code. ]
]

255/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: x86/highmem: Add a "already used pte" check
Date: Mon, 11 Mar 2013 17:09:55 +0100

This is a copy from kmap_atomic_prot().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

256/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: arm/highmem: Flush tlb on unmap
Date: Mon, 11 Mar 2013 21:37:27 +0100

The tlb should be flushed on unmap and thus make the mapping entry
invalid. This is only done in the non-debug case which does not look
right.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

257/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: arm: Enable highmem for rt
Date: Wed, 13 Feb 2013 11:03:11 +0100

fixup highmem for ARM.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

258/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: scsi/fcoe: Make RT aware.
Date: Sat, 12 Nov 2011 14:00:48 +0100

Do not disable preemption while taking sleeping locks. All user look safe
for migrate_diable() only.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

259/298 [
Author: Peter Zijlstra
Email: peterz@infradead.org
Subject: x86: crypto: Reduce preempt disabled regions
Date: Mon, 14 Nov 2011 18:19:27 +0100

Restrict the preempt disabled regions to the actual floating point
operations and enable preemption for the administrative actions.

This is necessary on RT to avoid that kfree and other operations are
called with preemption disabled.

Reported-and-tested-by: Carsten Emde <cbe@osadl.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

260/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: crypto: Reduce preempt disabled regions, more algos
Date: Fri, 21 Feb 2014 17:24:04 +0100

Don Estabrook reported
| kernel: WARNING: CPU: 2 PID: 858 at kernel/sched/core.c:2428 migrate_disable+0xed/0x100()
| kernel: WARNING: CPU: 2 PID: 858 at kernel/sched/core.c:2462 migrate_enable+0x17b/0x200()
| kernel: WARNING: CPU: 3 PID: 865 at kernel/sched/core.c:2428 migrate_disable+0xed/0x100()

and his backtrace showed some crypto functions which looked fine.

The problem is the following sequence:

glue_xts_crypt_128bit()
{
	blkcipher_walk_virt(); /* normal migrate_disable() */

	glue_fpu_begin(); /* get atomic */

	while (nbytes) {
		__glue_xts_crypt_128bit();
		blkcipher_walk_done(); /* with nbytes = 0, migrate_enable()
					* while we are atomic */
	};
	glue_fpu_end() /* no longer atomic */
}

and this is why the counter get out of sync and the warning is printed.
The other problem is that we are non-preemptible between
glue_fpu_begin() and glue_fpu_end() and the latency grows. To fix this,
I shorten the FPU off region and ensure blkcipher_walk_done() is called
with preemption enabled. This might hurt the performance because we now
enable/disable the FPU state more often but we gain lower latency and
the bug is gone.

Reported-by: Don Estabrook <don.estabrook@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

261/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: crypto: limit more FPU-enabled sections
Date: Thu, 30 Nov 2017 13:40:10 +0100

Those crypto drivers use SSE/AVX/… for their crypto work and in order to
do so in kernel they need to enable the "FPU" in kernel mode which
disables preemption.
There are two problems with the way they are used:
- the while loop which processes X bytes may create latency spikes and
  should be avoided or limited.
- the cipher-walk-next part may allocate/free memory and may use
  kmap_atomic().

The whole kernel_fpu_begin()/end() processing isn't probably that cheap.
It most likely makes sense to process as much of those as possible in one
go. The new *_fpu_sched_rt() schedules only if a RT task is pending.

Probably we should measure the performance those ciphers in pure SW
mode and with this optimisations to see if it makes sense to keep them
for RT.

This kernel_fpu_resched() makes the code more preemptible which might hurt
performance.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

262/298 [
Author: Mike Galbraith
Email: efault@gmx.de
Subject: crypto: scompress - serialize RT percpu scratch buffer access with a local lock
Date: Wed, 11 Jul 2018 17:14:47 +0200

| BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:974
| in_atomic(): 1, irqs_disabled(): 0, pid: 1401, name: cryptomgr_test
| Preemption disabled at:
| [<ffff00000849941c>] scomp_acomp_comp_decomp+0x34/0x1a0
| CPU: 21 PID: 1401 Comm: cryptomgr_test Tainted: G        W        4.16.18-rt9-rt #1
| Hardware name: www.cavium.com crb-1s/crb-1s, BIOS 0.3 Apr 25 2017
| Call trace:
|  dump_backtrace+0x0/0x1c8
|  show_stack+0x24/0x30
|  dump_stack+0xac/0xe8
|  ___might_sleep+0x124/0x188
|  rt_spin_lock+0x40/0x88
|  zip_load_instr+0x44/0x170 [thunderx_zip]
|  zip_deflate+0x184/0x378 [thunderx_zip]
|  zip_compress+0xb0/0x130 [thunderx_zip]
|  zip_scomp_compress+0x48/0x60 [thunderx_zip]
|  scomp_acomp_comp_decomp+0xd8/0x1a0
|  scomp_acomp_compress+0x24/0x30
|  test_acomp+0x15c/0x558
|  alg_test_comp+0xc0/0x128
|  alg_test.part.6+0x120/0x2c0
|  alg_test+0x6c/0xa0
|  cryptomgr_test+0x50/0x58
|  kthread+0x134/0x138
|  ret_from_fork+0x10/0x18

Mainline disables preemption to serialize percpu scratch buffer access,
causing the splat above.  Serialize with a local lock for RT instead.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

263/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: crypto: cryptd - add a lock instead preempt_disable/local_bh_disable
Date: Thu, 26 Jul 2018 18:52:00 +0200

cryptd has a per-CPU lock which protected with local_bh_disable() and
preempt_disable().
Add an explicit spin_lock to make the locking context more obvious and
visible to lockdep. Since it is a per-CPU lock, there should be no lock
contention on the actual spinlock.
There is a small race-window where we could be migrated to another CPU
after the cpu_queue has been obtain. This is not a problem because the
actual ressource is protected by the spinlock.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

264/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: panic: skip get_random_bytes for RT_FULL in init_oops_id
Date: Tue, 14 Jul 2015 14:26:34 +0200

Disable on -RT. If this is invoked from irq-context we will have problems
to acquire the sleeping lock.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

265/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: x86: stackprotector: Avoid random pool on rt
Date: Thu, 16 Dec 2010 14:25:18 +0100

CPU bringup calls into the random pool to initialize the stack
canary. During boot that works nicely even on RT as the might sleep
checks are disabled. During CPU hotplug the might sleep checks
trigger. Making the locks in random raw is a major PITA, so avoid the
call on RT is the only sensible solution. This is basically the same
randomness which we get during boot where the random pool has no
entropy and we rely on the TSC randomnness.

Reported-by: Carsten Emde <carsten.emde@osadl.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

266/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: random: Make it work on rt
Date: Tue, 21 Aug 2012 20:38:50 +0200

Delegate the random insertion to the forced threaded interrupt
handler. Store the return IP of the hard interrupt handler in the irq
descriptor and feed it into the random generator as a source of
entropy.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

267/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: random: avoid preempt_disable()ed section
Date: Fri, 12 May 2017 15:46:17 +0200

extract_crng() will use sleeping locks while in a preempt_disable()
section due to get_cpu_var().
Work around it with local_locks.

Cc: stable-rt@vger.kernel.org # where it applies to
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

268/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: cpu/hotplug: Implement CPU pinning
Date: Wed, 19 Jul 2017 17:31:20 +0200

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

269/298 [
Author: Mike Galbraith
Email: efault@gmx.de
Subject: sched: Allow pinned user tasks to be awakened to the CPU they pinned
Date: Sun, 19 Aug 2018 08:28:35 +0200

Since commit 7af443ee16976 ("sched/core: Require cpu_active() in
select_task_rq(), for user tasks") select_fallback_rq() will BUG() if
the CPU to which a task has pinned itself and pinned becomes
!cpu_active() while it slept.
The task will continue running on the to-be-removed CPU and will remove
itself from the CPU during takedown_cpu() (while cpuhp_pin_lock will be
acquired) and move to another CPU based on its mask after the
migrate_disable() section has been left.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

270/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: hotplug: duct-tape RT-rwlock usage for non-RT
Date: Fri, 4 Aug 2017 18:31:00 +0200

This type is only available on -RT. We need to craft something for
non-RT. Since the only migrate_disable() user is -RT only, there is no
damage.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

271/298 [
Author: Priyanka Jain
Email: Priyanka.Jain@freescale.com
Subject: net: Remove preemption disabling in netif_rx()
Date: Thu, 17 May 2012 09:35:11 +0530

1)enqueue_to_backlog() (called from netif_rx) should be
  bind to a particluar CPU. This can be achieved by
  disabling migration. No need to disable preemption

2)Fixes crash "BUG: scheduling while atomic: ksoftirqd"
  in case of RT.
  If preemption is disabled, enqueue_to_backog() is called
  in atomic context. And if backlog exceeds its count,
  kfree_skb() is called. But in RT, kfree_skb() might
  gets scheduled out, so it expects non atomic context.

3)When CONFIG_PREEMPT_RT_FULL is not defined,
 migrate_enable(), migrate_disable() maps to
 preempt_enable() and preempt_disable(), so no
 change in functionality in case of non-RT.

-Replace preempt_enable(), preempt_disable() with
 migrate_enable(), migrate_disable() respectively
-Replace get_cpu(), put_cpu() with get_cpu_light(),
 put_cpu_light() respectively

Signed-off-by: Priyanka Jain <Priyanka.Jain@freescale.com>
Acked-by: Rajan Srivastava <Rajan.Srivastava@freescale.com>
Cc: <rostedt@goodmis.orgn>
Link: http://lkml.kernel.org/r/1337227511-2271-1-git-send-email-Priyanka.Jain@freescale.com



Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

272/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: net: Another local_irq_disable/kmalloc headache
Date: Wed, 26 Sep 2012 16:21:08 +0200

Replace it by a local lock. Though that's pretty inefficient :(

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

273/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: net/core: protect users of napi_alloc_cache against reentrance
Date: Fri, 15 Jan 2016 16:33:34 +0100

On -RT the code running in BH can not be moved to another CPU so CPU
local variable remain local. However the code can be preempted
and another task may enter BH accessing the same CPU using the same
napi_alloc_cache variable.
This patch ensures that each user of napi_alloc_cache uses a local lock.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

274/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: net: netfilter: Serialize xt_write_recseq sections on RT
Date: Sun, 28 Oct 2012 11:18:08 +0100

The netfilter code relies only on the implicit semantics of
local_bh_disable() for serializing wt_write_recseq sections. RT breaks
that and needs explicit serialization here.

Reported-by: Peter LaDow <petela@gocougs.wsu.edu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

275/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: net: Add a mutex around devnet_rename_seq
Date: Wed, 20 Mar 2013 18:06:20 +0100

On RT write_seqcount_begin() disables preemption and device_rename()
allocates memory with GFP_KERNEL and grabs later the sysfs_mutex
mutex. Serialize with a mutex and add use the non preemption disabling
__write_seqcount_begin().

To avoid writer starvation, let the reader grab the mutex and release
it when it detects a writer in progress. This keeps the normal case
(no reader on the fly) fast.

[ tglx: Instead of replacing the seqcount by a mutex, add the mutex ]

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

276/298 [
Author: Yong Zhang
Email: yong.zhang@windriver.com
Subject: lockdep: selftest: Only do hardirq context test for raw spinlock
Date: Mon, 16 Apr 2012 15:01:56 +0800

On -rt there is no softirq context any more and rwlock is sleepable,
disable softirq context test and rwlock+irq test.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Yong Zhang <yong.zhang@windriver.com>
Link: http://lkml.kernel.org/r/1334559716-18447-3-git-send-email-yong.zhang0@gmail.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

277/298 [
Author: Josh Cartwright
Email: josh.cartwright@ni.com
Subject: lockdep: selftest: fix warnings due to missing PREEMPT_RT conditionals
Date: Wed, 28 Jan 2015 13:08:45 -0600

"lockdep: Selftest: Only do hardirq context test for raw spinlock"
disabled the execution of certain tests with PREEMPT_RT_FULL, but did
not prevent the tests from still being defined.  This leads to warnings
like:

  ./linux/lib/locking-selftest.c:574:1: warning: 'irqsafe1_hard_rlock_12' defined but not used [-Wunused-function]
  ./linux/lib/locking-selftest.c:574:1: warning: 'irqsafe1_hard_rlock_21' defined but not used [-Wunused-function]
  ./linux/lib/locking-selftest.c:577:1: warning: 'irqsafe1_hard_wlock_12' defined but not used [-Wunused-function]
  ./linux/lib/locking-selftest.c:577:1: warning: 'irqsafe1_hard_wlock_21' defined but not used [-Wunused-function]
  ./linux/lib/locking-selftest.c:580:1: warning: 'irqsafe1_soft_spin_12' defined but not used [-Wunused-function]
  ...

Fixed by wrapping the test definitions in #ifndef CONFIG_PREEMPT_RT_FULL
conditionals.

Signed-off-by: Josh Cartwright <josh.cartwright@ni.com>
Signed-off-by: Xander Huff <xander.huff@ni.com>
Acked-by: Gratian Crisan <gratian.crisan@ni.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

278/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: sched: Add support for lazy preemption
Date: Fri, 26 Oct 2012 18:50:54 +0100

It has become an obsession to mitigate the determinism vs. throughput
loss of RT. Looking at the mainline semantics of preemption points
gives a hint why RT sucks throughput wise for ordinary SCHED_OTHER
tasks. One major issue is the wakeup of tasks which are right away
preempting the waking task while the waking task holds a lock on which
the woken task will block right after having preempted the wakee. In
mainline this is prevented due to the implicit preemption disable of
spin/rw_lock held regions. On RT this is not possible due to the fully
preemptible nature of sleeping spinlocks.

Though for a SCHED_OTHER task preempting another SCHED_OTHER task this
is really not a correctness issue. RT folks are concerned about
SCHED_FIFO/RR tasks preemption and not about the purely fairness
driven SCHED_OTHER preemption latencies.

So I introduced a lazy preemption mechanism which only applies to
SCHED_OTHER tasks preempting another SCHED_OTHER task. Aside of the
existing preempt_count each tasks sports now a preempt_lazy_count
which is manipulated on lock acquiry and release. This is slightly
incorrect as for lazyness reasons I coupled this on
migrate_disable/enable so some other mechanisms get the same treatment
(e.g. get_cpu_light).

Now on the scheduler side instead of setting NEED_RESCHED this sets
NEED_RESCHED_LAZY in case of a SCHED_OTHER/SCHED_OTHER preemption and
therefor allows to exit the waking task the lock held region before
the woken task preempts. That also works better for cross CPU wakeups
as the other side can stay in the adaptive spinning loop.

For RT class preemption there is no change. This simply sets
NEED_RESCHED and forgoes the lazy preemption counter.

 Initial test do not expose any observable latency increasement, but
history shows that I've been proven wrong before :)

The lazy preemption mode is per default on, but with
CONFIG_SCHED_DEBUG enabled it can be disabled via:

 # echo NO_PREEMPT_LAZY >/sys/kernel/debug/sched_features

and reenabled via

 # echo PREEMPT_LAZY >/sys/kernel/debug/sched_features

The test results so far are very machine and workload dependent, but
there is a clear trend that it enhances the non RT workload
performance.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

279/298 [
Author: Mike Galbraith
Email: umgwanakikbuti@gmail.com
Subject: ftrace: Fix trace header alignment
Date: Sun, 16 Oct 2016 05:08:30 +0200

Line up helper arrows to the right column.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
[bigeasy: fixup function tracer header]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

280/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: x86: Support for lazy preemption
Date: Thu, 1 Nov 2012 11:03:47 +0100

Implement the x86 pieces for lazy preempt.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

281/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: arm: Add support for lazy preemption
Date: Wed, 31 Oct 2012 12:04:11 +0100

Implement the arm pieces for lazy preempt.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

282/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: powerpc: Add support for lazy preemption
Date: Thu, 1 Nov 2012 10:14:11 +0100

Implement the powerpc pieces for lazy preempt.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

283/298 [
Author: Anders Roxell
Email: anders.roxell@linaro.org
Subject: arch/arm64: Add lazy preempt support
Date: Thu, 14 May 2015 17:52:17 +0200

arm64 is missing support for PREEMPT_RT. The main feature which is
lacking is support for lazy preemption. The arch-specific entry code,
thread information structure definitions, and associated data tables
have to be extended to provide this support. Then the Kconfig file has
to be extended to indicate the support is available, and also to
indicate that support for full RT preemption is now available.

Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
]

284/298 [
Author: Mike Galbraith
Email: umgwanakikbuti@gmail.com
Subject: connector/cn_proc: Protect send_msg() with a local lock on RT
Date: Sun, 16 Oct 2016 05:11:54 +0200

|BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:931
|in_atomic(): 1, irqs_disabled(): 0, pid: 31807, name: sleep
|Preemption disabled at:[<ffffffff8148019b>] proc_exit_connector+0xbb/0x140
|
|CPU: 4 PID: 31807 Comm: sleep Tainted: G        W   E   4.8.0-rt11-rt #106
|Call Trace:
| [<ffffffff813436cd>] dump_stack+0x65/0x88
| [<ffffffff8109c425>] ___might_sleep+0xf5/0x180
| [<ffffffff816406b0>] __rt_spin_lock+0x20/0x50
| [<ffffffff81640978>] rt_read_lock+0x28/0x30
| [<ffffffff8156e209>] netlink_broadcast_filtered+0x49/0x3f0
| [<ffffffff81522621>] ? __kmalloc_reserve.isra.33+0x31/0x90
| [<ffffffff8156e5cd>] netlink_broadcast+0x1d/0x20
| [<ffffffff8147f57a>] cn_netlink_send_mult+0x19a/0x1f0
| [<ffffffff8147f5eb>] cn_netlink_send+0x1b/0x20
| [<ffffffff814801d8>] proc_exit_connector+0xf8/0x140
| [<ffffffff81077f71>] do_exit+0x5d1/0xba0
| [<ffffffff810785cc>] do_group_exit+0x4c/0xc0
| [<ffffffff81078654>] SyS_exit_group+0x14/0x20
| [<ffffffff81640a72>] entry_SYSCALL_64_fastpath+0x1a/0xa4

Since ab8ed951080e ("connector: fix out-of-order cn_proc netlink message
delivery") which is v4.7-rc6.

Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

285/298 [
Author: Mike Galbraith
Email: umgwanakikbuti@gmail.com
Subject: drivers/block/zram: Replace bit spinlocks with rtmutex for -rt
Date: Thu, 31 Mar 2016 04:08:28 +0200

They're nondeterministic, and lead to ___might_sleep() splats in -rt.
OTOH, they're a lot less wasteful than an rtmutex per page.

Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

286/298 [
Author: Mike Galbraith
Email: umgwanakikbuti@gmail.com
Subject: drivers/zram: Don't disable preemption in zcomp_stream_get/put()
Date: Thu, 20 Oct 2016 11:15:22 +0200

In v4.7, the driver switched to percpu compression streams, disabling
preemption via get/put_cpu_ptr(). Use a per-zcomp_strm lock here. We
also have to fix an lock order issue in zram_decompress_page() such
that zs_map_object() nests inside of zcomp_stream_put() as it does in
zram_bvec_write().

Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
[bigeasy: get_locked_var() -> per zcomp_strm lock]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

287/298 [
Author: Haris Okanovic
Email: haris.okanovic@ni.com
Subject: tpm_tis: fix stall after iowrite*()s
Date: Tue, 15 Aug 2017 15:13:08 -0500

ioread8() operations to TPM MMIO addresses can stall the cpu when
immediately following a sequence of iowrite*()'s to the same region.

For example, cyclitest measures ~400us latency spikes when a non-RT
usermode application communicates with an SPI-based TPM chip (Intel Atom
E3940 system, PREEMPT_RT_FULL kernel). The spikes are caused by a
stalling ioread8() operation following a sequence of 30+ iowrite8()s to
the same address. I believe this happens because the write sequence is
buffered (in cpu or somewhere along the bus), and gets flushed on the
first LOAD instruction (ioread*()) that follows.

The enclosed change appears to fix this issue: read the TPM chip's
access register (status code) after every iowrite*() operation to
amortize the cost of flushing data to chip across multiple instructions.

Signed-off-by: Haris Okanovic <haris.okanovic@ni.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

288/298 [
Author: Julia Cartwright
Email: julia@ni.com
Subject: watchdog: prevent deferral of watchdogd wakeup on RT
Date: Fri, 28 Sep 2018 21:03:51 +0000

When PREEMPT_RT_FULL is enabled, all hrtimer expiry functions are
deferred for execution into the context of ktimersoftd unless otherwise
annotated.

Deferring the expiry of the hrtimer used by the watchdog core, however,
is a waste, as the callback does nothing but queue a kthread work item
and wakeup watchdogd.

It's worst then that, too: the deferral through ktimersoftd also means
that for correct behavior a user must adjust the scheduling parameters
of both watchdogd _and_ ktimersoftd, which is unnecessary and has other
side effects (like causing unrelated expiry functions to execute at
potentially elevated priority).

Instead, mark the hrtimer used by the watchdog core as being _HARD to
allow it's execution directly from hardirq context.  The work done in
this expiry function is well-bounded and minimal.

A user still must adjust the scheduling parameters of the watchdogd
to be correct w.r.t. their application needs.

Cc: Guenter Roeck <linux@roeck-us.net>
Reported-and-tested-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Reported-by: Tim Sander <tim@krieglstein.org>
Signed-off-by: Julia Cartwright <julia@ni.com>
Acked-by: Guenter Roeck <linux@roeck-us.net>
[bigeasy: use only HRTIMER_MODE_REL_HARD]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

289/298 [
Author: Mike Galbraith
Email: umgwanakikbuti@gmail.com
Subject: drm,radeon,i915: Use preempt_disable/enable_rt() where recommended
Date: Sat, 27 Feb 2016 08:09:11 +0100

DRM folks identified the spots, so use them.

Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-rt-users <linux-rt-users@vger.kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

290/298 [
Author: Mike Galbraith
Email: umgwanakikbuti@gmail.com
Subject: drm,i915: Use local_lock/unlock_irq() in intel_pipe_update_start/end()
Date: Sat, 27 Feb 2016 09:01:42 +0100

[    8.014039] BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:918
[    8.014041] in_atomic(): 0, irqs_disabled(): 1, pid: 78, name: kworker/u4:4
[    8.014045] CPU: 1 PID: 78 Comm: kworker/u4:4 Not tainted 4.1.7-rt7 #5
[    8.014055] Workqueue: events_unbound async_run_entry_fn
[    8.014059]  0000000000000000 ffff880037153748 ffffffff815f32c9 0000000000000002
[    8.014063]  ffff88013a50e380 ffff880037153768 ffffffff815ef075 ffff8800372c06c8
[    8.014066]  ffff8800372c06c8 ffff880037153778 ffffffff8107c0b3 ffff880037153798
[    8.014067] Call Trace:
[    8.014074]  [<ffffffff815f32c9>] dump_stack+0x4a/0x61
[    8.014078]  [<ffffffff815ef075>] ___might_sleep.part.93+0xe9/0xee
[    8.014082]  [<ffffffff8107c0b3>] ___might_sleep+0x53/0x80
[    8.014086]  [<ffffffff815f9064>] rt_spin_lock+0x24/0x50
[    8.014090]  [<ffffffff8109368b>] prepare_to_wait+0x2b/0xa0
[    8.014152]  [<ffffffffa016c04c>] intel_pipe_update_start+0x17c/0x300 [i915]
[    8.014156]  [<ffffffff81093b40>] ? prepare_to_wait_event+0x120/0x120
[    8.014201]  [<ffffffffa0158f36>] intel_begin_crtc_commit+0x166/0x1e0 [i915]
[    8.014215]  [<ffffffffa00c806d>] drm_atomic_helper_commit_planes+0x5d/0x1a0 [drm_kms_helper]
[    8.014260]  [<ffffffffa0171e9b>] intel_atomic_commit+0xab/0xf0 [i915]
[    8.014288]  [<ffffffffa00654c7>] drm_atomic_commit+0x37/0x60 [drm]
[    8.014298]  [<ffffffffa00c6fcd>] drm_atomic_helper_plane_set_property+0x8d/0xd0 [drm_kms_helper]
[    8.014301]  [<ffffffff815f77d9>] ? __ww_mutex_lock+0x39/0x40
[    8.014319]  [<ffffffffa0053b3d>] drm_mode_plane_set_obj_prop+0x2d/0x90 [drm]
[    8.014328]  [<ffffffffa00c8edb>] restore_fbdev_mode+0x6b/0xf0 [drm_kms_helper]
[    8.014337]  [<ffffffffa00cae49>] drm_fb_helper_restore_fbdev_mode_unlocked+0x29/0x80 [drm_kms_helper]
[    8.014346]  [<ffffffffa00caec2>] drm_fb_helper_set_par+0x22/0x50 [drm_kms_helper]
[    8.014390]  [<ffffffffa016dfba>] intel_fbdev_set_par+0x1a/0x60 [i915]
[    8.014394]  [<ffffffff81327dc4>] fbcon_init+0x4f4/0x580
[    8.014398]  [<ffffffff8139ef4c>] visual_init+0xbc/0x120
[    8.014401]  [<ffffffff813a1623>] do_bind_con_driver+0x163/0x330
[    8.014405]  [<ffffffff813a1b2c>] do_take_over_console+0x11c/0x1c0
[    8.014408]  [<ffffffff813236e3>] do_fbcon_takeover+0x63/0xd0
[    8.014410]  [<ffffffff81328965>] fbcon_event_notify+0x785/0x8d0
[    8.014413]  [<ffffffff8107c12d>] ? __might_sleep+0x4d/0x90
[    8.014416]  [<ffffffff810775fe>] notifier_call_chain+0x4e/0x80
[    8.014419]  [<ffffffff810779cd>] __blocking_notifier_call_chain+0x4d/0x70
[    8.014422]  [<ffffffff81077a06>] blocking_notifier_call_chain+0x16/0x20
[    8.014425]  [<ffffffff8132b48b>] fb_notifier_call_chain+0x1b/0x20
[    8.014428]  [<ffffffff8132d8fa>] register_framebuffer+0x21a/0x350
[    8.014439]  [<ffffffffa00cb164>] drm_fb_helper_initial_config+0x274/0x3e0 [drm_kms_helper]
[    8.014483]  [<ffffffffa016f1cb>] intel_fbdev_initial_config+0x1b/0x20 [i915]
[    8.014486]  [<ffffffff8107912c>] async_run_entry_fn+0x4c/0x160
[    8.014490]  [<ffffffff81070ffa>] process_one_work+0x14a/0x470
[    8.014493]  [<ffffffff81071489>] worker_thread+0x169/0x4c0
[    8.014496]  [<ffffffff81071320>] ? process_one_work+0x470/0x470
[    8.014499]  [<ffffffff81076606>] kthread+0xc6/0xe0
[    8.014502]  [<ffffffff81070000>] ? queue_work_on+0x80/0x110
[    8.014506]  [<ffffffff81076540>] ? kthread_worker_fn+0x1c0/0x1c0

Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-rt-users <linux-rt-users@vger.kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

291/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: drm/i915: disable tracing on -RT
Date: Thu, 6 Dec 2018 09:52:20 +0100

Luca Abeni reported this:
| BUG: scheduling while atomic: kworker/u8:2/15203/0x00000003
| CPU: 1 PID: 15203 Comm: kworker/u8:2 Not tainted 4.19.1-rt3 #10
| Call Trace:
|  rt_spin_lock+0x3f/0x50
|  gen6_read32+0x45/0x1d0 [i915]
|  g4x_get_vblank_counter+0x36/0x40 [i915]
|  trace_event_raw_event_i915_pipe_update_start+0x7d/0xf0 [i915]

The tracing events use trace_i915_pipe_update_start() among other events
use functions acquire spin locks. A few trace points use
intel_get_crtc_scanline(), others use ->get_vblank_counter() wich also
might acquire a sleeping lock.

Based on this I don't see any other way than disable trace points on RT.

Cc: stable-rt@vger.kernel.org
Reported-by: Luca Abeni <lucabe72@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

292/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: drm/i915: skip DRM_I915_LOW_LEVEL_TRACEPOINTS with NOTRACE
Date: Wed, 19 Dec 2018 10:47:02 +0100

The order of the header files is important. If this header file is
included after tracepoint.h was included then the NOTRACE here becomes a
nop. Currently this happens for two .c files which use the tracepoitns
behind DRM_I915_LOW_LEVEL_TRACEPOINTS.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

293/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: cgroups: use simple wait in css_release()
Date: Fri, 13 Feb 2015 15:52:24 +0100

To avoid:
|BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:914
|in_atomic(): 1, irqs_disabled(): 0, pid: 92, name: rcuc/11
|2 locks held by rcuc/11/92:
| #0:  (rcu_callback){......}, at: [<ffffffff810e037e>] rcu_cpu_kthread+0x3de/0x940
| #1:  (rcu_read_lock_sched){......}, at: [<ffffffff81328390>] percpu_ref_call_confirm_rcu+0x0/0xd0
|Preemption disabled at:[<ffffffff813284e2>] percpu_ref_switch_to_atomic_rcu+0x82/0xc0
|CPU: 11 PID: 92 Comm: rcuc/11 Not tainted 3.18.7-rt0+ #1
| ffff8802398cdf80 ffff880235f0bc28 ffffffff815b3a12 0000000000000000
| 0000000000000000 ffff880235f0bc48 ffffffff8109aa16 0000000000000000
| ffff8802398cdf80 ffff880235f0bc78 ffffffff815b8dd4 000000000000df80
|Call Trace:
| [<ffffffff815b3a12>] dump_stack+0x4f/0x7c
| [<ffffffff8109aa16>] __might_sleep+0x116/0x190
| [<ffffffff815b8dd4>] rt_spin_lock+0x24/0x60
| [<ffffffff8108d2cd>] queue_work_on+0x6d/0x1d0
| [<ffffffff8110c881>] css_release+0x81/0x90
| [<ffffffff8132844e>] percpu_ref_call_confirm_rcu+0xbe/0xd0
| [<ffffffff813284e2>] percpu_ref_switch_to_atomic_rcu+0x82/0xc0
| [<ffffffff810e03e5>] rcu_cpu_kthread+0x445/0x940
| [<ffffffff81098a2d>] smpboot_thread_fn+0x18d/0x2d0
| [<ffffffff810948d8>] kthread+0xe8/0x100
| [<ffffffff815b9c3c>] ret_from_fork+0x7c/0xb0

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

294/298 [
Author: Mike Galbraith
Email: efault@gmx.de
Subject: cpuset: Convert callback_lock to raw_spinlock_t
Date: Sun, 8 Jan 2017 09:32:25 +0100

The two commits below add up to a cpuset might_sleep() splat for RT:

8447a0fee974 cpuset: convert callback_mutex to a spinlock
344736f29b35 cpuset: simplify cpuset_node_allowed API

BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:995
in_atomic(): 0, irqs_disabled(): 1, pid: 11718, name: cset
CPU: 135 PID: 11718 Comm: cset Tainted: G            E   4.10.0-rt1-rt #4
Hardware name: Intel Corporation BRICKLAND/BRICKLAND, BIOS BRHSXSD1.86B.0056.R01.1409242327 09/24/2014
Call Trace:
 ? dump_stack+0x5c/0x81
 ? ___might_sleep+0xf4/0x170
 ? rt_spin_lock+0x1c/0x50
 ? __cpuset_node_allowed+0x66/0xc0
 ? ___slab_alloc+0x390/0x570 <disables IRQs>
 ? anon_vma_fork+0x8f/0x140
 ? copy_page_range+0x6cf/0xb00
 ? anon_vma_fork+0x8f/0x140
 ? __slab_alloc.isra.74+0x5a/0x81
 ? anon_vma_fork+0x8f/0x140
 ? kmem_cache_alloc+0x1b5/0x1f0
 ? anon_vma_fork+0x8f/0x140
 ? copy_process.part.35+0x1670/0x1ee0
 ? _do_fork+0xdd/0x3f0
 ? _do_fork+0xdd/0x3f0
 ? do_syscall_64+0x61/0x170
 ? entry_SYSCALL64_slow_path+0x25/0x25

The later ensured that a NUMA box WILL take callback_lock in atomic
context by removing the allocator and reclaim path __GFP_HARDWALL
usage which prevented such contexts from taking callback_mutex.

One option would be to reinstate __GFP_HARDWALL protections for
RT, however, as the 8447a0fee974 changelog states:

The callback_mutex is only used to synchronize reads/updates of cpusets'
flags and cpu/node masks. These operations should always proceed fast so
there's no reason why we can't use a spinlock instead of the mutex.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

295/298 [
Author: Sebastian Andrzej Siewior
Email: bigeasy@linutronix.de
Subject: apparmor: use a locallock instead preempt_disable()
Date: Wed, 11 Oct 2017 17:43:49 +0200

get_buffers() disables preemption which acts as a lock for the per-CPU
variable. Since we can't disable preemption here on RT, a local_lock is
lock is used in order to remain on the same CPU and not to have more
than one user within the critical section.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
]

296/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: workqueue: Prevent deadlock/stall on RT
Date: Fri, 27 Jun 2014 16:24:52 +0200

Austin reported a XFS deadlock/stall on RT where scheduled work gets
never exececuted and tasks are waiting for each other for ever.

The underlying problem is the modification of the RT code to the
handling of workers which are about to go to sleep. In mainline a
worker thread which goes to sleep wakes an idle worker if there is
more work to do. This happens from the guts of the schedule()
function. On RT this must be outside and the accessed data structures
are not protected against scheduling due to the spinlock to rtmutex
conversion. So the naive solution to this was to move the code outside
of the scheduler and protect the data structures by the pool
lock. That approach turned out to be a little naive as we cannot call
into that code when the thread blocks on a lock, as it is not allowed
to block on two locks in parallel. So we dont call into the worker
wakeup magic when the worker is blocked on a lock, which causes the
deadlock/stall observed by Austin and Mike.

Looking deeper into that worker code it turns out that the only
relevant data structure which needs to be protected is the list of
idle workers which can be woken up.

So the solution is to protect the list manipulation operations with
preempt_enable/disable pairs on RT and call unconditionally into the
worker code even when the worker is blocked on a lock. The preemption
protection is safe as there is nothing which can fiddle with the list
outside of thread context.

Reported-and_tested-by: Austin Schuh <austin@peloton-tech.com>
Reported-and_tested-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://vger.kernel.org/r/alpine.DEB.2.10.1406271249510.5170@nanos


Cc: Richard Weinberger <richard.weinberger@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
]

297/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: signals: Allow rt tasks to cache one sigqueue struct
Date: Fri, 3 Jul 2009 08:44:56 -0500

To avoid allocation allow rt tasks to cache one sigqueue struct in
task struct.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

298/298 [
Author: Thomas Gleixner
Email: tglx@linutronix.de
Subject: Add localversion for -RT release
Date: Fri, 8 Jul 2011 20:25:16 +0200

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
]

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

This patch adds pinctrl support for cannonlake.

Signed-off-by: Pradhan Surya Narayanx <surya.narayanx.pradhan@intel.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

Both the qemux86 and qemux86-64 targets RRECOMMEND the ens1370 kernel
module and set QB_AUDIO_OPT to support that as one of the audio cards as
well.

Fixes: daadaf7f ("yocto-kernel-cache: [PATCH] Update audio support v2")
Signed-off-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

1/1 [
Author: Richard Purdie
Email: richard.purdie@linuxfoundation.org
Subject: arm/Makefile: Fix systemtap
Date: Sun, 10 Mar 2019 06:43:15 +0000

Currently systemtap fails to operate correctly on armv7 systems such as beaglebone and
soon, qemuarm.

root@qemuarm:/usr/src/kernel# env -uARCH -uKBUILD_EXTMOD -uCROSS_COMPILE -uKBUILD_IMAGE -uKCONFIG_CONFIG -uINSTALL_PATH -uLD_LIBRARY_PATH PATH=/usr/bin:/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin make -C /lib/modules/4.19.19-yocto-standard/build M=/tmp/staptcNU6M modules CONFIG_DEBUG_INFO= CONFIG_STACK_VALIDATION= ARCH=arm stap_4321_src.i --no-print-directory -j2 V=1
test -e include/generated/autoconf.h -a -e include/config/auto.conf || (		\
echo >&2;							\
echo >&2 "  ERROR: Kernel configuration is invalid.";		\
echo >&2 "         include/generated/autoconf.h or include/config/auto.conf are missing.";\
echo >&2 "         Run 'make oldconfig && make prepare' on kernel src to fix it.";	\
echo >&2 ;							\
/bin/false)
mkdir -p /tmp/staptcNU6M/.tmp_versions ; rm -f /tmp/staptcNU6M/.tmp_versions/*
make -f ./scripts/Makefile.build obj=/tmp/staptcNU6M
(cat /dev/null;   echo kernel//tmp/staptcNU6M/stap_4321.ko;) > /tmp/staptcNU6M/modules.order
  gcc -Wp,-MD,/tmp/staptcNU6M/.stap_4321_src.o.d  -nostdinc -isystem /usr/lib/gcc/arm-poky-linux-gnueabi/8.3.0/include -I./arch/arm/include -I./arch/arm/include/generated  -I./include -I./arch/arm/include/uapi -I./arch/arm/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/kconfig.h -include ./include/linux/compiler_types.h -D__KERNEL__ -mlittle-endian -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -fshort-wchar -Werror-implicit-function-declaration -Wno-format-security -std=gnu89 -fno-PIE -DCC_HAVE_ASM_GOTO -fno-dwarf2-cfi-asm -fno-omit-frame-pointer -mapcs -mno-sched-prolog -fno-ipa-sra -mabi=aapcs-linux -mfpu=vfp -funwind-tables -marm -Wa,-mno-warn-deprecated -D__LINUX_ARM_ARCH__=7 -march=armv5t -Wa,-march=armv7-a -msoft-float -Uarm -fno-delete-null-pointer-checks -Wno-frame-address -Wno-format-truncation -Wno-format-overflow -Wno-int-in-bool-context -Os -Wno-maybe-uninitialized --param=allow-store-data-races=0 -Wframe-larger-than=1024 -fstack-protector-strong -Wno-unused-but-set-variable -Wno-unused-const-variable -fno-omit-frame-pointer -fno-optimize-sibling-calls -fno-var-tracking-assignments -pg -Wdeclaration-after-statement -Wno-pointer-sign -Wno-stringop-truncation -fno-strict-overflow -fno-merge-all-constants -fmerge-constants -fno-stack-check -fconserve-stack -Werror=implicit-int -Werror=strict-prototypes -Werror=date-time -Werror=incompatible-pointer-types -Werror=designated-init -fmacro-prefix-map=./= -Wno-packed-not-aligned -Iinclude2/asm/mach-default -I/lib/modules/4.19.19-yocto-standard/build -include /tmp/staptcNU6M/stapconf_4321.h -D "STP_NO_VELREL_CHECK" -freorder-blocks -fasynchronous-unwind-tables -Wframe-larger-than=512 -fno-ipa-icf -Wno-unused -Wno-tautological-compare -Werror -I/usr/share/systemtap/runtime  -DMODULE  -DKBUILD_BASENAME='"stap_4321_src"' -DKBUILD_MODNAME='"stap_4321"' -c -o /tmp/staptcNU6M/stap_4321_src.o /tmp/staptcNU6M/stap_4321_src.c
/tmp/ccaE9CMG.s: Assembler messages:
/tmp/ccaE9CMG.s:49: Error: selected processor does not support `dmb ish' in ARM mode
/tmp/ccaE9CMG.s:52: Error: architectural extension `mp' is not allowed for the current b

(which was from running the stap command with -v -v -v -k and then being able to run the command individually)

Note that it says armv5t above.

That comes from the code this patch changes

root@qemuarm:/usr/src/kernel# gcc -march=armv7-a /tmp/staptcNU6M/stap_4321_aux_0.c
cc1: error: -mfloat-abi=hard: selected processor lacks an FPU

which makes me wonder if cc-option fails unless -mfpu-vfp is on the commandline too.

Since we have a gcc which accepts the armv7-a arch, just remove the cc-option
wrapper unconditionally here.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>